STUDIES IN GLOBAL ARCHAEOLOGY 22

Technology, Ideology and Environment

The Social Dynamics of Iron Metallurgy in Great Zimbabwe, AD 900 to the Present

Ezekia Mtetwa

Department of Archaeology and Ancient History Uppsala, Sweden

2017

Dissertation presented at Uppsala University to be publicly examined in Geijersalen, Engelskaparken, Thunbergsvägen 3H, Uppsala, Friday, 19 January 2018 at 13:00 for the degree ofDoctor of Philosophy. The examination will be conducted in English. Faculty examiner:Professor Bertram Mapunda (University of Dar es Salaam, College of Arts and SocialSciences).

AbstractMtetwa, E. 2017. Technology, Ideology and Environment. The Social Dynamics of IronMetallurgy in Great Zimbabwe, AD 900 to the Present. Studies in Global Archaeology 22.84 pp. Uppsala: Department of Archaeology and Ancient History. ISBN 978-91-506-2591-2.

This thesis provides insights into the nature and organization of iron technology associatedwith past and present communities of Great Zimbabwe in southern Africa. Written accounts,ethnographic enquiries and, results of archaeological field surveys and excavations arecombined to provide the first detailed account of Great Zimbabwe’s iron productiontechnologies. The existence of a considerable iron industry in Great Zimbabwe with complexand innovative designs and processes of iron smelting is established. Evidence includes tapslags, natural draft furnaces, one with a unique rectangular morphology, and the exploitationof manganese-rich iron ores or fluxes. Moderate to low levels of iron oxide in slag samplespoint to large-scale production of good quality iron for an extensive market at some time in thepast of Great Zimbabwe. Iron slags, possible bloom pieces and broken tuyeres are examinedusing standard archaeometallurgical laboratory techniques to establish the decisions and choicesunderlying technology and pyro-metallurgical processes in and between sites. The results areexplained using theoretical concepts of social practice and agency to address the worldviews,social values and beliefs of iron related practices in Great Zimbabwe over time.

The study provides an alternative angle for approaching the social complexity of GreatZimbabwe (with its peak in the 12th–16th centuries AD), previously understood from theperspective of its spectacular architecture. Evidence of primary and secondary productionactivities in domestic and specialized settings outside settlements suggests a greaterspatiotemporal complexity and ambiguity of the organization of technology than previouslythought. Iron production in domestic contexts provided an inclusive space, creating thepossibility for transformation of not just materials, but also women and children into socialagents of technology, adding an alternative and more socially embedded perspective oftechnology in Africa.

Keywords: Great Zimbabwe, Iron Metallurgy, Urbanism, Innovation, Landscape, SocialDynamics, Natural Draft, Forced Draft, Southern Africa, Archaeometallurgy, Anthracology,Archaeometry

Ezekia Mtetwa, Department of Archaeology and Ancient History, African and ComparativeArchaeology, Box 626, Uppsala University, SE-75126 Uppsala, Sweden.

© Ezekia Mtetwa 2017

ISSN 1651-1255ISBN 978-91-506-2591-2urn:nbn:se:uu:diva-334799 (http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-334799)

To my loving and supportive wife StellaPriscilla, my sweet-spirited sons Ezekiel

Anesuishe and Jesimiel Asher,And to

My inspiring parents Wilson Qedisani andEdnah Zinyanga, including my eleven sib-

lings, whom I all missed throughout thisstudy – may your joy be full.

List of Papers

This thesis is based on the following papers, which are referred to in the text by Roman numerals.

I. Mtetwa, E. In review. Iron metallurgy in the Great Zimbabwe hinterland: new archaeometallurgical field evidence, AZANIA: Archaeological Research in Africa.

II. Mtetwa, E. In review. The bloomery iron technologies of Great Zimbabwe from AD 1000 – an archaeometallurgy of social practices. Journal of Archaeological Science.

III. Mtetwa, E and Lindahl, A. manuscript. The Archaeometry of Tuyeres from Great Zimbabwe and Wider Implications for its Iron Production Technologies. To be submitted to the Archae-ometry journal

IV. Mtetwa, E. In press. Great Zimbabwe’s iron: its technological materials and social space. In: Pikirayi, I (ed.) The World of Great Zimbabwe. New York: Routledge (peer reviewed)

V. Mtetwa, E., Maposa, Y. C., Manyanga, M., & Chirikure, S. (2017). When the smith is a woman: innovation, improvisation and ambiguity in the organisation of African iron metallurgy. In: Manyanga, M. and Chirikure, S. (eds.), Archives, Objects, Places and Landscapes: Multidisciplinary approaches to De-colonised Zimbabwean pasts, 295-318. Bamenda: Langaa RPCIG.

Reprints were made with permission from the respective publishers.

Contents

1  Introduction ......................................................................................... 13 1.1  Aims of the dissertation .................................................................. 13 1.2. Theoretical framework ...................................................................... 14 1.3. Synopsis of the papers ....................................................................... 17 

2  Background .......................................................................................... 20 2.1  Physical and socio-cultural background .......................................... 20 

2.1.1  The geology and mineral resources ....................................... 20 2.1.2  Topography and Drainage ..................................................... 23 2.1.3  Settlement history .................................................................. 25 2.1.4  Vegetation .............................................................................. 26 

2.2  Previous research on iron technology in Great Zimbabwe ............. 28 2.2.1  The Great Zimbabwe urban centre ........................................ 28 2.2.2  Looking beyond the urban centre .......................................... 30 

2.3  New investigations in the hinterland of Great Zimbabwe ............... 31 

3  Methodology and material ................................................................... 33 3.1  Ethnography and written record ...................................................... 33 

3.1.1  Direct observations and interviews ........................................ 34 3.2  Archaeology .................................................................................... 35 

3.2.1  Legacy Collections ................................................................ 35 3.2.2  Community Archaeology: a brief note .................................. 36 3.2.3  Archaeological field surveys ................................................. 36 3.2.4  Archaeological excavations ................................................... 37 

3.3  Archaeometallurgy .......................................................................... 48 3.3.1  Visual and Macroscopic observations ................................... 48 3.3.2  Microscopic and chemical analyses of slags and piece of iron bloom ............................................................................................ 48 

3.4  Archaeometry of metallurgical ceramics ........................................ 49 3.4.1  Materials and methods ........................................................... 49 

3.5  Archaeobotany – an anthracological approach ............................... 51 3.5.1  Material .................................................................................. 51 3.5.2  Method ................................................................................... 52 

4  Results ................................................................................................. 53 4.1  Evidence from written records: smelting techniques, organization and ritual practices ................................................................................... 53 4.2  Existing Collections ........................................................................ 54 4.3  Evidence from archaeological field surveys and excavations ......... 55 

4.3.1  Boroma Excavations .............................................................. 57 4.3.2  Veza 1 Excavations ................................................................ 57 4.3.3  Mutevedzi Excavations .......................................................... 58 

4.4  Results for chemical and microstructural analyses ......................... 59 4.4.1  Mashava ................................................................................. 59 4.4.2  Mutevedzi .............................................................................. 59 4.4.3  Boroma .................................................................................. 60 4.4.4  Sviba ...................................................................................... 60 4.4.5  Veza A Site ............................................................................ 61 4.4.6  Veza B Site ............................................................................ 61 4.4.7  Chigaramboni ........................................................................ 62 4.4.8  Goose Bay .............................................................................. 62 

4.5  Evidence from Anthracological analysis ........................................ 63 4.5.1  Boroma Site ........................................................................... 63 4.5.2  Veza A Site ............................................................................ 65 4.5.3  Goose Bay Site....................................................................... 65 

5  Discussion ............................................................................................ 67 5.1  Spatial and social organization ....................................................... 67 5.2  Technological variability ................................................................ 68 5.3  Variation and change in resource exploitation patterns .................. 70 

6  Conclusion and future research ........................................................... 73 

References ..................................................................................................... 75 

Acknowledgements

My most sincere gratitudes go, first, to my two supervisors, Paul Sinclair and Anneli Ekblom, who helped me to remain focused and yet open-minded throughout the study. Paul joined me in two of my fieldworks in Zimbabwe and I benefited immensely from his long-term experience in the archaeology of Great Zimbabwe in particular and Africa in general. Anneli Ekblom also, trained me in the practical aspects of Environmental Archaeology (among sev-eral other courses), which became one of the invaluable skills in my teaching responsibilities in the Department, but also in the PhD study itself. I also owe them a huge debt of gratitude for their magnanimous funding and support in competing for supplementary internal scholarships advertised within Uppsala University. Paul, for instance, paid for my training costs in archaeomtallurgy while Anneli raised funds for all the printing costs. Still on funding, I am equally grateful for the financial support generously given by my Department of Archaeology and Ancient History, the Societas Archaeologica Upsaliensis (SAU), and the British Institute in Eastern Africa (BIEA) among others.

I also would like to thank all the members of the Department for creating an accommodative work and study environment for me throughout the dura-tion of my PhD. Both senior researchers and fellow doctoral colleagues in-spired my interests in varied theoretical aspects, themes and methods in Global Archaeology via organized seminars, workshops, excursions, lectures, and in-formal fika theory discussions. Our staff in the IT, Accounts and Human Re-sources departments were equally helpful. Elisabet Green, for example, intro-duced me to the health system in Uppsala city and helped me recover from a few but acute health challenges in the early months of my stay in Sweden. With my family, we drew upon the social strength of the camaraderie spirit in the PhD Association in the Department to recover from the stress of a miscar-riage at the peak of writing this thesis, tack så jätte mycket kära kollegor!

I am equally indebted to Eva-Hjärthner-Holdar and her colleagues at the Geo-Archaeological Laboratory (GAL), particularly Lena Grandin and Erik Ogenhall, who trained me in laboratory analyses of metallurgical materials with great patience. They also gave rich comments for one of my papers sub-mitted for publication. Anders Lindahl also, trained me in aspects of ceramic analysis at Lund University’s Department of Geology, Sweden. Many thanks also go to all the individuals who commented on several other papers in this study, including the institutions that gave me permission to compile them into a thesis. Although I acknowledge them in some of the papers making up this

thesis, once more, I would like to reiterate my gratitude to the institutions in Zimbabwe whose support made the fieldwork possible and successful. The National Museums and Monuments of Zimbabwe (NMMZ) and the traditional leaders around Great Zimbabwe gave me the necessary permits to conduct archaeological surveys and excavations. I am also grateful to staff members and students from the University of Zimbabwe, Midlands State University, Great Zimbabwe University as well as NMMZ who assisted me in the field. Finally yet importantly, I am forever indebted to my loving wife Stella and our two awesome sons, Ezekiel and Jesimiel, who endured my swinging moods, a gloomy face and absence (mentally and physically) especially in the final year of this study. Together with my parents and siblings, I owe you lots of smiles, giggles, laughter, and importantly, the innumerable gains of our first Doctoral Degree in the clan. Ndinomubonga yaemho mweshe!

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1 Introduction

1.1 Aims of the dissertation I explore two mutually inclusive themes in this PhD thesis. The first is the nature of iron technology in Great Zimbabwe, one of the earliest and largest societies in southern Africa that experienced significant technological and so-ciopolitical transformations from c. AD 900. The second concerns the possi-bility of illuminating the changing worldviews, social values and cultural at-titudes shaping and reshaped by iron related practices in Great Zimbabwe from c. AD 900 to the present. To that end, I examine material traces of indig-enous iron metallurgy recovered from the wider archaeological landscape sur-rounding the urban centre to establish the key parameters of the technology, including the social organization of current smithing activities. My intention is to reveal technological variability in the iron metallurgy of Great Zimbabwe over time, which I explain as materializing broad scale changes in the social values and ideologies of the people of Great Zimbabwe over time. As such, I use the theoretical concepts of social agency and materiality to articulate the interrelated engagements within and between humans and their biophysical world. The following specific objectives further crystallize my research ques-tions:

To examine variability in the iron production technologies of

the Great Zimbabwe area

To determine the spatial and social organization of iron related practices in the wider archaeological landscape of Great Zimba-bwe over time.

To illuminate the dynamics of human-environment interactions in iron-related practices, particularly the social engagement with wood resources for metallurgical processes.

In sub-Saharan Africa at least, the production, consumption and circulation of iron are socially textured phenomena (see detailed review in Chirikure, 2015). By focusing on the iron industry of Great Zimbabwe, therefore, I unravel crit-ical aspects of the everyday life of one of the earliest and largest societies associated with urbanism, social complexity and statehood in southern Africa.

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For more than a century, researchers recurrently focused on the impressive architecture and space within the urban centre, essentially blurring the possi-bility of viewing settlement from the angle of its iron related practices. My study, therefore, can be seen as an answer to the numerous calls by varied scholars of Great Zimbabwe such as Garlake (1978), Sinclair (1987), Ndoro (2001), Fontein (2006) and Chirikure and Pikirayi (2008) to look beyond the impressive walls in conducting the archaeology of the drystone-built-capital. In their different research agendas, these scholars have challenged upcoming researchers like me, to take a renewed and more vigorous interest in the di-verse material culture of Great Zimbabwe in developing an enriched and co-herent history of the settlement.

In light of the above calls, enviable research efforts have already been in-vested in a variety of artefacts found within the constituent walled enclosures of the Great Zimbabwe urban centre (e.g. Bandama et al., 2017; Chirikure and Pikirayi, 2008; Herbert 1996; Matenga, 2011; Miller, 2002). One conspicuous omission, however, is the lack of focused research on the dynamics of social interactions established between the Great Zimbabwe urban centre and com-munities in the hinterland over time, especially in iron related practices. We lack a clear understanding of how the inhabitants of the Great Zimbabwe area socially engaged with each other across space and the surrounding biophysical landscape in the specialized production and consumption of iron – and other materials. The social and physical use of the immediate and broader landscape of Great Zimbabwe was undoubtedly an integral component in the people’s everyday idea of the world and social life. In this study, therefore, I bring for-ward the significance of iron in the large-scale social, economic, political and environmental systems and processes of Great Zimbabwe. I also illuminate the hinterland of the prehistoric urban centre as a crucial section of the places making up the social networks that sustained the urban centre over a long pe-riod in mutual interactions.

1.2. Theoretical framework

Iron technology, in this study, is reconstructed and theorized as a dynamic process of mutual transformation between people and their material world in the everyday social practices of Great Zimbabwe, a notion inspired by Marcia-Anne Dobres (2000). Most important in this respect is the continuation of some indigenous iron related practices into our modern-day contexts in the form of casting and forging of scrap metals. These provide daily scenarios for conceptualizing crafts production practices within the broader context of changing social, economic, political and environmental systems and processes of modern-day rural and urban life in Zimbabwe. Great Zimbabwe is associ-ated with the origins of social complexity, urbanism and statehood in southern Africa, reaching its zenith in the mid second millennium AD (Chirikure et al.,

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2016; Huffman, 2014; Pikirayi, 2001). It bears marks of a sophisticated worldview characterized by the construction of drystone monumental archi-tecture and consumption of a wide range of exotica from active participation in global trade. Such prosperity is understood to have developed on the back-drop of a solid agro-pastoral economy, land availability, religion, and a unique skill in crafts production and architectural engineering (Pikirayi 2017; Moffett & Chirikure 2016; Sinclair et al. 2012; Chipunza 1994; Garlake 1973; Pwiti 1991). The monumental architecture and disparate arts, interpreted elsewhere as conspicuous consumption (see Trigger, 2003), indicate the appropriation of high levels of skills and ideology and materials to produce and transform the social space of Great Zimbabwe (see also Matenga, 2011; Pikirayi, 2013).

The production of iron, therefore, is viewed as an integral component of the technological and sociopolitical transformations of Great Zimbabwe, which began towards the end of the first millennium AD in southern Africa (Mitchell, 2002; Phillipson, 2005). I view the material remains recovered within and around Great Zimbabwe’s urban centre, including the current smithing activities, as materializing changes in the people’s worldviews, so-cial values and belief systems. This line of thought also builds on Conkey's (1993) thesis, that humans are materialists and symbolists simultaneously. Perhaps one of the most vivid examples depicting such a dual persona in the people of Great Zimbabwe is their use of blocks of banded ironstone to deco-rate one of the walls near the famous Conical Tower in the Great Enclosure of Great Zimbabwe. This illustration is just one example showing the ceremonial consumption of iron, even in its ore state. Another example is the ceremonial and utilitarian iron objects recovered from the urban centre, which have re-ceived considerable research attention (e.g. Chirikure, 2015, 2007, Herbert, 1996). As such, the remains of iron production debris explored in this study could provide a window of opportunity to address the shortfall in our knowledge of the cultural attitudes towards iron in Great Zimbabwe. Until now, iron, as a category of material culture has received very little archaeo-logical attention in comparison to the reasonably well researched stone archi-tecture, soapstone birds and figurines (Huffman, 1996; Matenga, 2011; 1993).

Because of my focus on the social dynamics of technology, the theories of social practice and agency as inspired by Pierre Bourdieu (1977) and Anthony Giddens (1984) are of central interest. An emphasis in these theories on the influence of the habitus, here referring to the worldview, social beliefs and values in shaping an agent’s actions and thoughts is critical for illuminating how iron related practices are socially textured. I am equally interested in Henri Lefebvre’s (1991) notions of social space and materiality as pursued and developed by a number of researchers in the last decades (see detailed review in Witmore, 2014) to unravel the archaeologies of Great Zimbabwe’s iron. Thus, an understanding of iron technology as both a material and social space in which varied social agents co-existed has the potential to illuminate how unequal social power relations were negotiated in iron related practices.

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Within socio-political and economic systems such as that of Great Zimbabwe, the appropriation of natural resources and manipulation of embodied techno-logical knowledge in human agents tend to be highly contested social space, a phenomenon commonly encountered in the past and present societies of the world (Lefebvre 1991). The conventional view in the archaeology of African iron metallurgy has emphasized that such materials as reproductive organs de-picted on furnaces and tuyeres, for example, are indicative of the politics of exclusion of women as agents of ritualized technology (e.g. Herbert, 1993; Killick, 1990). Through the conceptual tools highlighted, I intend to provide an alternative account of Great Zimbabwe’s iron industry based on data sets some of which were unrecorded in previous researches.

Another important aspect theorized in this study is the spatial location of iron production, given that this had wider implications for the social organi-zation of iron technology in terms of the configuration and reconfiguration of gender identities encompassed in technology (see Dobres et al., 1995). I do believe that the location of iron production within the domestic arena provided a context in which women and possibly children would have been socialized or negotiated their way into the world of iron, emerging as technological agents. Likewise, by entering into the domestic sphere, I will argue, iron pro-duction would have fitted into a broader fertility worldview materialized in organs of the female anatomy depicted on houses, pots, drums and headrests (Collett 1993; Chirikure 2005). This way of viewing these decoration crosso-vers has the potential to provide an alternative reading of iron technology in which female agency is far more prominent than currently projected. Some of the domestic contexts within the urban centre and wider archaeological land-scape of Great Zimbabwe have yielded evidence of small-scale iron produc-tion, characterized by a rich application of external surface treatments and decorations of the bloomery furnaces (e.g. Bent, 1893; Sinclair, 1984). I con-trast these materials with large-scale iron production sites concentrated in the hinterland, which lack traceable surface treatments but have significant inter-nal ritual embodiments of the furnaces (e.g. Mtetwa, 2011).

So far, iron related practices in Great Zimbabwe have been understood and interpreted on the basis of the material traces recovered within the urban centre (Miller 2002; Herbert 1996; Bandama et al. 2016a). There remains a blurred picture of the social interactions established between the hinterland and the urban centre itself. The recurrent focus on metallurgical assemblages within the urban centre continues to give a false impression of technology as elitist, given that the main site of Great Zimbabwe was an important political, reli-gious and trade centre. This is a phenomenon common in urban studies (see Wynne-Jones 2007:377). Wynne Jones’ (2007) studied ceramics in the urban–rural areas of the Swahili regions and observed that people were producing and using articles of daily life, and that consumption patterns were similar across the urban/rural divide (Wynne-Jones 2007:377). The unequal distribu-tion of such resources as iron ore and woodlands across the Great Zimbabwe

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landscape underscore the fact that both the elite and non-elite inhabitants of Great Zimbabwe’s seamless material space exploited the same resources. As explained by Lefebvre (1991), such a material space is an arena of interaction and convergence by various groups in which the rhythms of everyday life would have shaped and reshaped the production and appropriation of the so-cial and material world.

Al Idrisi, writing around AD 1154, reports a thriving trade along the coast in iron obtained from the interior of southern Africa which he described as excelling that from India in quantity, quality and malleability (Prendergast, 1974). His remarks have the potential to show how the physical quality of southern Africa’s iron, as a materiality, made social interactions with the other distant parts of the world to emerge. Conkey (1993) aptly described humans, our species, as materialists and symbolists simultaneously, which emphasizes the inseparability of the social and material world. A common theme among the varied approaches of materiality is that material things and social practices bring each other into being and are analytically indivisible (Jones 2004; Joyce & Joyce 2015; Witmore 2014). Witmore (2014), however, insists that material things should be prioritized for study in archaeology, not as backdrops of hu-man lifeways, but for the reason that they are participants/actors with their own emergence and existence. This emphasis on materiality as an active agent helps me to approach the various groups of materials that actively participated in the iron production process and systems of Great Zimbabwe.

I conceptualize the archaeological and ethnographic contexts explored in this study suggestive of women’s active participation in technology arena as historical realities that are often not factored when negotiating modern-day social spaces laden with unequal dimensions of gender representation. I intend to use some of my archaeological results and the ethnographic case of Mrs. Khohliwe Zanhi, a female smith discussed in Paper V, to mount an exhibition at the Mining, Engineering, and Transport Expo showing the role of women and traditional iron technology in the social reproduction of Zimbabwe’s mod-ern-day society. Thus, for me, the study of preindustrial iron technology is another way of approaching and contributing to the transformation of the so-cial constitution of technology in my own modern-day world.

1.3. Synopsis of the papers

There are five papers making up this PhD thesis with each one of them ex-ploring a specific theme under the overarching study of the dynamics of iron provisioning systems and processes in Great Zimbabwe from as early as AD 900 to the present.

Paper I (Mtetwa, E. in review) presents for the first time, detailed examples of iron metallurgy in the wider archaeological landscape of Great Zimbabwe

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recovered from previous and current research. The paper gives the empirical background and grounding of this PhD thesis. Prior to this study, areas sur-rounding the urban centre were said to have a dearth of iron production debris. However as reviewed in this paper, previous excavations and surveys and also those presented in the course of this thesis project is now challenging this un-derstanding. The paper reviews the evidence of different practices of iron tech-nology in and around Great Zimbabwe. The growing number of recorded iron production sites and the different technological practices they embody pro-vides a new understanding of the physical and social use of the Great Zimba-bwe landscape. The paper reports the presence of a thriving industry in the wider archaeological landscape in the form of clusters of large circular furnace bases, heaps of tuyeres fused in multiple tap and flow slags, magnetite iron ores, including a rectangular furnace base.

Paper 11 (Mtetwa, E. in review) deals with the chemical and microstructural characteristics of the varied types of slags using ICP-AES and ICP-MS anal-yses techniques and a possible bloom sample analyzed metallographically. These data are used to identify and reconstruct the nature of technological de-cisions ironworkers undertook regarding raw materials, pyrometallurgical processes and key technological parameters in Zimbabwe. The results demon-strate the presence of sophisticated iron production technologies in the form of slag tapping, natural draft and varied fluxing techniques, which possibly included the addition of bones and other plant materials within ritualized con-texts.

Paper III (Mtetwa, E and Lindahl, A. manuscript) discusses the XRF results of metallurgical tuyeres from different sites across the Great Zimbabwe land-scape some of which were fused in multiples indicative of natural draft iron technology. Results show striking similarities and differences in clay re-sources selected for use between neighboring sites, suggesting the tendency to share resources as a cultural value, but also the adaptation of technology to local resources and cultural choices. The dominance of grains in the silt and sand fractions, which are a natural components of the clay selected, points to the time and skill invested in prospecting for clays that are self-tempered. On the other hand, the presence of crushed grains in the coarse sand and fine gravel in a few samples reflect the ability to deliberately correct the plasticity of clay whenever the naturally tempered clay sources were scarce in a partic-ular area or over time. The paper also highlights how the selection and prepa-ration of clays for ceramic technology would have had a direct contribution in the slag-metal separation, particularly in smelting iron ores with few gangue materials of their own.

Paper IV (Mtetwa, E. in press) makes use of the new archaeological field ev-idence to illuminate variation and change in the social organization of iron

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technology in Great Zimbabwe. The iron production sites located within do-mestic contexts are drawn upon to argue for household-based production. This household-based production, it is argued would have included the whole household, including women. The paper also discusses that household pro-duction may have been a means to socialize children into the social world and technological skills related to iron production. Household-based production is also drawn upon to argue for transmission of technological skills along family lines, as observed in similar encounters in Sub-Saharan Africa. The use of large natural draft furnaces, which represents a significant change in tech-niques of iron production, is also considered to be indicative of change in the worldview of iron and iron related practices. The presence of literature indi-cating the uniqueness of natural draft to sub-Saharan Africa helps to dismiss biases in 19th century written records, which associated novel designs and pro-cesses of iron technology to European ancestry.

Paper V (Mtetwa et al., 2017) uses an ethnographic case study to problematize the conventional projection of iron technology as a male domain, a position that is common in global archaeology. By highlighting the contemporary re-ality of a female chief smith near Great Zimbabwe, the paper brings out the complexity and ambiguity of the social organization of technology and makes parallels with iron technology in the past based on written sources. The paper calls for theories and methods that treats women as agents of technology in prehistoric, modern and future contexts.

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2 Background

2.1 Physical and socio-cultural background In this chapter, I introduce the biophysical world of Great Zimbabwe, which was integral to the everyday life of its inhabitants and their neighbors in south-ern Africa. I consider, particular, aspects of the environment that are crucial to iron production and other cultural practices surrounding it. Although my focus lies on the geography of present day Zimbabwe in general and Great Zimbabwe in particular, the territory that fell under the influence of the latter was far bigger in the past. As pointed out by Ekblom et al (in press), the social networks of places under Great Zimbabwe would have included the region demarcated by the Mozambican coastal lowlands on the east. The Kalahari Desert bordered it to the west while the Soutpansberg range of mountains and the southern fringes of central Africa made its southern and northern limits respectively (see Chirikure et al., 2017).

2.1.1 The geology and mineral resources Zimbabwe is one of several sub-Saharan African countries richly endowed with a diversity of mineral wealth (Figure 1). Geologically, about two thirds of the country, just like the large areas of South Africa and Botswana, is un-derlain by the granite-greenstone complex that forms the Zimbabwe Craton (Moore et al., 2009). The Craton is a part of the ancient continent of Western Gondwana with rocks dating back to the early Archaeon Eon, about 3.46 bil-lion years ago (Wilson et al., 1995). It is intruded by Zimbabwe’s Great Dyke, a major linear layered mafic/ultramafic igneous complex, about 550 km in length, that cuts across the Zimbabwe Craton in a north-north-eastern direc-tion (Armstrong and Wilson, 2000). The Great Dyke (see Fig 1), which is 2.5 billion years old, like many other mafic intrusions, is associated with econom-ically important metals such as gold, chrome, nickel, copper, platinum, tita-nium, vanadium and tin. Importantly, it is also rich in iron ore deposits (Liu et al., 2014; Liu and Jin, 2014).

The diversified geology and richness of mineral resources of the Zimbabwe Craton have spawned a dynamic social engagement between humans and their material world since prehistoric times. During the Stone Age, the larger quartz and dolerite veins and dykes in the granite plutons of the Matopos, were quar-ried for the raw materials of varied lithic technologies (Walker, 1995). The

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mineral resources, on the other hand, especially iron, gold, copper, tin, and lead have been mined and processed for subsistence and exchange within and beyond the continent since the first millennium AD (Cline, 1937; Hall, 1905; Summers, 1969; Swan, 2008, 2007, 1994).

Figure 1. Map showing some of the minerals of Zimbabwe and the location of Great Zimbabwe (modified from http://www.lib.utexas.edu/maps/africa)

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Great Zimbabwe itself is situated on the southern edge of the Zimbabwe plat-eau within this Archaean complex of greenstones, mafic, ultramafic rocks, gneisses and migmatites, and late intrusive granites. Masvingo area as a whole is characterised by two forms of granite reliefs, gneissic granite which forms whalebacked hills and bornhardts, and the massive granite which gives rise to scattered castle kopjes, tors and dwalas (Lister, 1987). These formations have provided architectural foundations and granite blocks for monumental, stone-built structures associated with the Zimbabwe period (Pikirayi, 2001b).

Forming the skyline of the Great Zimbabwe landscape are the sharp ridges of the Nyanda, Nyuni and Beza Ranges that rise between 300 and 450 metres which are rich in banded ironstones and quartzites (Gwavava and Ranganai, 2009; Lister, 1987; Wilson, 1973). These iron-rich ores sustained premodern industrial iron metallurgy in the area from as early as the advent of metal-working and agro-pastoral communities in first millennium AD up to colonial times (Mtetwa 2011; Ndoro 1994). For instance, the Mount Buchwa area barely 100km west of Great Zimbabwe, has evidence of Matola/Silver Leaves pottery dated to the 3rd and 5th centuries AD, suggesting that its rich iron ore deposits attracted early metal working populations to this area (Huffman, 1978).

Matola/Silver Leaves pottery is associated with the spread of early farming communities into the interior of southern Africa during the first half of the first millennium AD (Mitchell and Whitelaw, 2005). In addition, Carl Mauch, a German explorer and geologist, who visited Great Zimbabwe in 1871, ob-served some smiths quarrying a chalk-slate containing ferruginous mica quar-ried from sources near the villages settlements, which they roasted, crushed, and reduced repeatedly over a period of one week (Burke and Mauch, 1969). He also observed that the ironworkers used the natural granite surfaces and stones to crush and reduce the ores into smaller fragments, demonstrating yet another social use of the Great Zimbabwe physiography landscape in pro-cessing and producing daily materials and artifacts.

The Zimbabwe Iron and Steel Company (ZISCO) and the Steelmakers Group Company, also known as SIMBI, are exploiting the rich iron deposits at Mount Buchwa and Nyuni Hills respectively. This indicates that the miner-als in the broader regional landscape of Great Zimbabwe are integral to the social life of past and present communities in southern Zimbabwe, connecting them to global trade throughout time. Similarly, areas near the Bondolfi Mis-sion, about 15km northwest of the Great Zimbabwe centre, have rich gold de-posits. These deposits supported precolonial gold mining from the end of the first millennium AD (Phimister 1976; 1974), and are being exploited today too. The extraction of minerals, even in modern-day contexts of most commu-nities in Sub-Saharan Africa, is embedded in cosmological and religious power structures, often replete with community and individual appeasement of ancestral spirits. These are viewed as owners of all mineral wealth and other

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natural resources and as such are believed to be rewarders of all mineral ex-traction, offering protecting against mining hazards and natural disasters (Chirikure, 2015).

2.1.2 Topography and Drainage Being located on the southern margins of the Zimbabwe plateau, the Great Zimbabwe and surrounding area straddles the highveld on the northern end and the middle veld to the south, the latter one an elevation between 600-1200 m above sea level (Kay, 1970). The Zimbabwe plateau (Fig 3), is a broad, southwest-northeast oriented topographic plateau, which forms the central wa-tershed of the country. It separates the Zambezi River basin to the north and the Limpopo and Save River basins to the south and southeast. The highvield is characterized by an old surface of a low undulating relief and long, flat ho-rizons, which, however, progressively increases in height to nearly 2600 m at the summit of Inyangani (Lister, 1987; Moore et al., 2009). The mountain ranges together with the Zimbabwe plateau make up the country’s highveld, a region of areas over 1200m above sea level (Kay, 1970).

Figure 2. The location of Great Zimbabwe on the margins of the higheld, and the agro-ecological zones of Zimbabwe (Modified from Hentze et al. 2016)

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The drainage systems are of high relevance for the understanding of iron-prac-tices and use of environment more broadly. There is a marked difference in the character of the river systems to the north and south of the Zimbabwe cen-tral watershed. Immediately north of the central watershed, the country is characterised by a mature drainage network, with meandering rivers and low gradients in broad shallow valleys (Lister, 1987), providing more surface wa-ter to local communities. In contrast, the rivers to the south of the central wa-tershed, oriented southeasterly, are younger in age and characterised by steeper gradients as well as more deeply incised, rectilinear courses. A typical example is the Mutirikwi River, the largest and longest in the Great Zimbabwe catchment, which carries very small amounts of water because of rapid run-off generated by a steep gradient from the hilly terrain. As such, groundwater is the major source of consumable water in the Great Zimbabwe area, a sce-nario obtaining in many rural areas of Zimbabwe (Maclear et al., 2002). A recent study of the Great Zimbabwe area’s current water consumption and conservation patterns discovered an abundance of natural springs, with some of them active throughout the year (Pikirayi et al., 2016). These natural springs, would have provided the much-needed water for metallurgical activ-ities apart from domestic consumption and watering of livestock.

Figure 3. The drainage system of Zimbabwe and major rivers crossing the Great Zimbabwe landscape (modified from Moore et al 2009)

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Compared to the adjacent Limpopo and Save lowvelds, which receive less than 600mm of rainfall per annum (Manyanga, 2006), the Great Zimbabwe urban centre and immediate vicinities enjoy a favorable microclimate – pos-sibly a function of past human activity. Much of the rain comes in the form of mist, locally known as guti, which, together with its numerous natural springs, as mentioned above, make the Great Zimbabwe area a water-rich landscape that supports the production of grain and other crops (Bannerman 1982; Pikirayi 2001; Pikirayi et al. 2016). The hilly topography around the urban centre, in particular, precipitates moisture from prevailing southeasterly winds, resulting in a mean annual precipitation of between 800-1000 mm, which is relatively sufficient for crop production. Thus, such a local climate, an easily tilled soil, ample timber and firewood as well as small game would have attracted varying population groups to settle in the Great Zimbabwe over millennia (Garlake, 1973).

2.1.3 Settlement history

The geological features in the area have been an integral part to the lifeworld of the Great Zimbabwe inhabitants over time, both when it comes to ironmak-ing practices, as will be discussed here, but also older practices of ritual and representation of a society’s worldview. Rock art sites such as Chamavara and Chesvingo near Great Zimbabwe indicate an intimate interplay between the worldview of hunter-gatherers and the physical formations of Great Zimba-bwe’s granite landscape. As generally observed across the Zimbabwe plateau and adjacent lowlands, Late Stone Age hunter-gatherer communities (c. 13 000 to 1 500 years ago) seem to have been pursuing a semi-sedentary life-style, as evidenced by storage pits in rocky hills and grindstones in their set-tlements (Jonsson, 1998; Walker, 1995). Though of limited extent, rock art is found on panels and shelters around Great Zimbabwe, similar to the more ex-tensive rock-art sites found in other parts of Zimbabwe and southern Africa as a whole (Garlake, 1982; Lewis-Williams et al., 2000; Walker, 1995). The cul-tivable land and fertile loamy soils in the narrow valleys between the numer-ous granite hills attracted the settlement and development of populations with an agro-pastoral lifestyle, attested in the Great Zimbabwe area from around the mid-first millennium AD (Bandama et al., 2016; Collett et al., 1992; Summers et al., 1961).

Towards the end of the first millennium AD, there was a gradual emergence of larger population and power centers in southern Africa (Sinclair 1987; Chirikure et al., 2013; Huffman, 2009; Kim and Kusimba, 2008). These were characterised by a novel drystone architecture that utilized the natural bedrock formations, a phenomenon lavishly demonstrated at Great Zimbabwe and such other urbanized centres as Khami, Naletale and Dlodlo in central Zimba-bwe. As pointed out by Ndoro (2001), the granite boulders, rock outcrops and shelters, which were incorporated into some of the stone enclosures of the

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urban centre, would have been crucial in materializing human perceptions of the world and social power (see also Pikirayi, 2013). In Shona worldview, such boulders are the abode of venerated ancestral spirits, which made Pikirayi (2013) argue that the construction of monumental architecture in the Zimba-bwe Culture involved the manipulation of ideology and nature to create social power (see also Knox, 1985).

2.1.4 Vegetation Secure access to wood resources is crucial for iron production and innovation. Unfortunately, there is still little data on long-term vegetation change in the region. Wild and Fernandes compiled the most detailed mapping of vegetation in Zimbabwe in the mid-20th century. The vegetation of the country today is predominantly Brachystegia-Julbernadia (miombo) woodlands, with large ar-eas of Colophospermum mopane (mopane) woodlands in the Zambezi basin in the north and the Limpopo basin in the south (Brenan et al., 1968; Hedberg and Hedberg, 1968; Müller, 1994). Areas in the west and south-west of the country are covered extensively by woodlands dominated by Acacia and Com-bretum species (Müller, 1994). The Save and Limpopo Basins to the southeast and south of Zimbabwe are dominated by mopane woodland (Colosphosper-mum mopane), well known for their timber and charcoal production (Wild and Fernandes 1968; Venter et al. 2003). The southern section of the Great Zim-babwe landscape, in particular around Mushandike, has an abundance of mo-pane woodlands. Archaeological charcoals from the urban centre and iron pro-duction sites have confirmed its popular use for domestic and metallurgical purposes (Chikumbirike, 2014), as will be discussed in more detail below.

Owing to a long-history of human settlement and considerable population size, traditionally estimated at 20 000 inhabitants (Huffman, 1996), it has been suggested that there have been significant changes in the condition and state of the vegetation of Great Zimbabwe (Figure 2). The assumption is that this open landscape was due to degradation by inhabitants of the Great Zimbabwe for domestic fuel, timber, and clearing of agricultural fields (see also Banner-man 1982). For Bannerman (1982), the population of Great Zimbabwe would have grown beyond the carrying capacity of the surrounding landscape, citing the absence of Brachystegia spiciformis within the urban centre as an example of environmental degradation. Studies of photographic records from Great Zimbabwe also show that vegetation was more open in the late 19th - early 20th century than today (see review in Chikumbirike 2014).

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Figure 4. Vegetation map of Zimbabwe showing the location of Great Zim-babwe (Modified from Hentze et al. 2016)

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However, these assumptions have not adequately factored in the vegetation management policies adopted by various regimes curating the Great Zimba-bwe monument right from the onset of colonial administration of the site around 1900 AD. The construction of a golf course around the monument at the height of colonial rule in Zimbabwe, for instance, also saw many more trees being cleared from the monument. Also, as a way of controlling vegeta-tion from affecting the drystone walls at the site, but also as a way of improv-ing the visibility of the walls for visitors, site managers have periodically cleared away trees and creepers from the monument ever since (Ndoro, 2001).

Studies conducted in southern Africa on savannas and savanna woodlands show that these tend to be ecologically unstable, given the region’s vulnera-bility to high incidences of rainfall variability within and between the rain seasons (Ekblom, 2012; Ekblom et al., 2012; Holmgren et al., 2012). Though research is still limited, some studies have made use of pollen records to re-construct human-environmental interactions and the results so far suggest that there is little evidence indicative of change in the forest taxa around population centers. One example is the study from Thulamela, one of the Zimbabwe tra-dition sites in South Africa dated between AD 1400 and 1650 (Ekblom et al., 2014). Chikumbirike’s analysis of archaeological charcoals recovered from within the Great Zimbabwe urban centre and Chigaramboni ironworking site also confirmed that there is no significant difference between the vegetation species reflected in the archaeological record and the contemporary landscape (Chikumbirike, 2014a). This suggests that woodland management strategies designed to enhance sustainable exploitation of varied forest taxa may have been more diversified and efficient than previously imagined. The numerous myths, taboos and legends associated with current vegetation resource man-agement strategies of such sacred groves as Norumedzo in Bikita near Great Zimbabwe provides an ethnographic reality crucial for understanding situa-tions in the deep past (e.g. Mawere, 2013, 2012). There is need for a more detailed research focusing on the environmental history of such local areas as Great Zimbabwe to augment the picture derived from regional studies high-lighted above, as another way of unlocking its past (see Pikirayi in press).

2.2 Previous research on iron technology in Great Zimbabwe

2.2.1 The Great Zimbabwe urban centre Paper I presents more detail on the research background. I summarize this discussion here for the benefit of the general reader. The earliest European visitors to southern Africa observed iron production technologies that were still in operation in the 19th and 20th centuries. In Great Zimbabwe, the earliest European observers, Carl Mauch and Theodore Bent for example, reported

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widely about the low shaft forced draft iron smelting technology, whose fur-naces and tuyeres were invariably sexualized (Bent, 1893; Burke and Mauch, 1969). Together with the local contemporaries, these earliest ethnographers’ reports excluded or poorly represented earlier types of iron technologies of Great Zimbabwe that were visible in the archaeological record of their locali-ties. For instance, Carl Mauch took notice of the presence of multiple fused tuyeres around Great Zimbabwe, but local contemporaries allegedly dismissed the iron production debris as stemming from an earlier generation of ‘white people’ credited with building the Great Zimbabwe (Burke & Mauch 1969: 136–137). Mauch and his local contemporaries highlighted the radically dif-ferent technological styles in the same locality over time, but associated a vis-ibly complex iron technology to a superior white race.

The encounter between archaeologists and the evidence of iron production started as early as the 1890s (Bent, 1892; Caton-Thompson, 1931; Hall, 1905; 1909; Willoughby, 1893). Together with other mundane materials at Great Zimbabwe such as pottery, these were viewed as essentially disconnected from the history of the site. David Randal MacIver was the first to assess all categories of material culture found within the stone ruins, including metal artifacts, from which he proposed the African authorship and medieval date of Great Zimbabwe for the first time (Randall-MacIver, 1906). Further exca-vations by Gertrude Caton-Thompson (1931) recovered a larger corpus of fin-ished iron weapons and tools which she also interpreted as of African shape and manufacture. While she acknowledged that the metal objects were soundly crafted, she thought, however, that metal alloys had been imported from outside (Caton-Thompson, 1931: 64). It was not believed that production had taken place locally. The recurrent focus on the Great Zimbabwe site as a foreign product during the early decades of research at the site obscured the significance of its iron production debris, which reflected the entire sequence of the iron production process. Chirikure & Pikirayi (2008) note that up until the 1980s, research at Great Zimbabwe remained biased by colonial under-standings, which obscured an understanding of the local history of metal pro-duction. In addition, the long period of vandalism that marked the early years of research at the site further fragmented the archaeological record of iron production within the site (Bandama et al., 2016a; Garlake, 1973; D Miller, 2002)

In the 1990s, Herbert (1996) took special interest in the growing corpus of iron production debris from previous surveys and excavations within the Great Zimbabwe centre. These artifacts represented the entire sequence of iron met-allurgy at the site in the form of iron ores, furnace rubbles, slags, metalworking equipment, finished tools and other metal objects (Herbert, 1996: 643–644). At the heart of Herbert’s studies was an attempt to understand the link between metals and power, mundanity and sacredness from the perspective of the given co-existence of daily utilitarian (e.g. hoes, axes, chisels) alongside more pres-tigious items such as spears and ceremonial axes. Her hypothesis proposing

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that primary metal extraction took place within royal spaces of the site formed an interesting line of research in later studies on the production, consumption and distribution of metals in Great Zimbabwe. In particular, Chirikure and colleagues set out to explore the spatial distribution of iron production debris from different sections of the urban centre, recovering more evidence of smelt-ing and smithing activities such as tuyeres with run-back slag and an assort-ment of other types of slag (Bandama et al., 2016a; Chirikure, 2015, 2007b; Fredriksen and Chirikure, 2015). These studies have shown that every section of Great Zimbabwe’s dry-stone-built capital bore remnants of metal extrac-tion, secondary smithing and finished products, which they think suggest household-based production by royal family members themselves (Chirikure 2007: 88; Bandama et al., 2016: 12).

2.2.2 Looking beyond the urban centre While the studies highlighted above reflect the complexity of the social organ-ization of iron technology within the urban centre, they overlooked the grow-ing number of recorded iron production sites in the hinterland, and how these related with the centre itself over time. In 1991, Webber Ndoro conducted archaeological surveys in an area 10 km west of the Great Zimbabwe site aim-ing to establish prehistoric settlement patterns and obtain a greater understand-ing of the wider cultural landscape around the prehistoric urban centre (Ndoro 1994). He identified 21 sites comprising one rock art paintings site, an Early Iron Age settlement, nine terminal Zimbabwe Culture sites and ten iron smelt-ing sites. These are located in the Chigaramboni mountain ranges, which lie on a north/south axis and form a plateau that continues to the Great Zimbabwe site. Brachystegia and Apocrynaceae tree species dominate the entire plateau while granite hills scattered on the same plateau are mainly of haematite iron-stones, which would have supported the development of metallurgical activi-ties in the area. Three of the recorded iron smelting sites consisted of a few furnace bases, very small amounts of slags and funnel shaped single tuyeres, which typically suggests the use of bellows driven furnaces (Chirikure et al. 2009). The other seven sites had large heaps of tuyeres and very thick pieces of collapsed dhaka furnace walls. As reported by Ndoro, many of the tuyeres were fused in multiples, some having more than ten pieces measuring 8 cm mean diameter on both ends indicative of natural draft iron smelting technol-ogies (Prendergast 1975; Killick 1991).

Even earlier, Paul Sinclair conducted rescue excavations at Gokomere Mis-sion, about 40km north of Great Zimbabwe, recovering a furnace decorated with breasts and dated to the turn of the 19th century AD (Sinclair 1984). The latter furnace contrasts sharply with those excavated by Ndoro in the Chi-garamboni hills, which had diameters as wide as 1.4 m in average and were concentrated in as many as five furnaces in one locality. The important point

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here is that Sinclair and Ndoro’s excavations revealed interesting technologi-cal variability and innovation in Great Zimbabwe, as observed in the history of African iron metallurgy (e.g. Cline, 1937; Killick, 1990; Mapunda, 1995). These new findings raise questions regarding the technological history of Great Zimbabwe in particular and southern Africa as a whole, which could not be asked from materials recovered from the urban centre.

Apart from Sinclair and Ndoro’s works mentioned above, a few other stud-ies are worth mentioning with regards iron metallurgy in the hinterland of the Great Zimbabwe urban centre and the country at large. Lorraine Swan con-ducted surveys in the Malilangwe Trust Estate, more than a 100km south-east of Great Zimbabwe (Swan, 2007; 2008a). She excavated both Early Farming and Zimbabwe Period iron working activities where two sites, Hlambamlonga and Mhangula, were seen as possible iron sources for the Great Zimbabwe state. The large-scale nature of these sites, the absence of any large settlement nearby and contemporaneity with Great Zimbabwe suggested that they sup-plied Great Zimbabwe with some of its iron (Swan, 2007). Of equal signifi-cance are the excavations conducted in other parts of Zimbabwe where mate-rials similar to those recovered around Great Zimbabwe have been discovered. Prendergast (Prendergast, 1979; 1975), for instance, discovered for the first time, the presence of natural draft furnaces in northern Zimbabwe dated to the 14th and 15th centuries AD. Again, Chirikure recorded extensive iron produc-tion sites in northern and eastern Zimbabwe reflecting greater variability, in-cluding the possible use of natural draft and slag tapping techniques at Swart Village site (AD 800 -1200). Within variation, these findings in northern Zim-babwe provide a general framework for conceptualizing the technology and chronology of archaeometallurgical materials discovered by Ndoro in the Chi-garamboni hills, a point that I will return to later on.

2.3 New investigations in the hinterland of Great Zimbabwe

In 2010, I received a report about an extensive large-scale iron working site near Gaths Mine in Mashava 40km north-west of Great Zimbabwe, which I investigated as part of my MA dissertation work with the University of Dar es Salaam in Tanzania. With the help of archaeology students from the Midlands State University in Zimbabwe, I conducted intensive foot surveys within a kilometre radius of the iron-smelting site. We identified at least twenty possi-ble furnace bases, each one measuring at least one metre in internal diameter and these were in association with large amounts of multiple fused tuyeres, blocky furnace rubble, and dense slags. Other slag pieces were cylindrical in shape and some were flat, bearing flow marks indicative of the use of slag

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tapping techniques at the site (Mtetwa, 2011). I discussed results of the tech-nological analyses of selected slag samples from this site, whose low levels of iron oxide indicate an efficient iron smelting approach. The materials under-pinned an intensive use of natural draught iron smelting technology akin to the materials discovered by Ndoro and Prendergast mentioned above. These few known examples of iron smelting technologies from Chigaramboni hills and Mashava sites inspired me to undertake a broader study of the iron metal-lurgy in the wider archaeological landscape of Great Zimbabwe for my PhD project with Uppsala University in Sweden. I deal with the various social and technical questions of the study in the five papers making up this thesis. In the next chapter, I address the data collection and analyses methods I adopted to explore the iron industry of Great Zimbabwe area.

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3 Methodology and material

The Great Zimbabwe cultural landscape carries, arguably, one of the most ex-tensive and diverse records of iron production technologies in southern Africa, as demonstrated in Paper I. The significance of these materials is that they are tangible traces for reaching and understanding of varied aspects of the every-day social practices of the Great Zimbabwe people over time. Importantly, unravelling the inseparable relationship between the material world and social meaning in past and present societies requires an inter-disciplinary approach, which straddles qualitative and quantitative research methods common in hu-manities and natural sciences respectively (Kothari, 2004). In this study, I combine a number of approaches in ethnography, community archaeology, archaeometallurgy, archaeometry and archaeobotany. My personal experi-ences of growing up in socio-cultural and environmental settings similar to those in modern-day contexts of the local communities around Great Zimba-bwe constituted yet another source of value to this study.

3.1 Ethnography and written record In studies of past iron production technologies of sub-Saharan Africa, ethnog-raphy has been a profitable approach in understanding and interpreting the social contexts within which iron related practices emerged and changed over time (Chirikure, 2005; Cline, 1937; David et al., 1989; Herbert, 1993; Humphris, 2010; Killick, 1990; Mathoho et al., 2016; Peter R Schmidt and Mapunda, 1997). Archaeologists have used some or all of the different ap-proaches found within ethnography such as oral traditions, direct historical testimonies, detailed observations, interviews as well as primary and second-ary documents to explore the societies’ worldviews, beliefs and cultural val-ues.

One of the session abstracts for the Eighth World Archaeological Congress (WAC-8) 2016 in Kyoto, Japan, under the theme of Science and Archaeology carried the title, “Social Archaeometallurgy: The Role of Metals within and between Societies.” The session organizers, Prof Mark Pollard and colleagues, remarked that the dominance of ethnography and anthropology in Africa and Latin America has tended to make archaeometallurgy more social than tech-nical (Pollard et al., 2016: 298-290). Interestingly, their call to discuss multi-ple issues embedded in social archaeometallurgy by researchers from different

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archaeometallurgical traditions echoes an earlier appeal made at another con-ference in 1996. In the Archaeology and Anthropology of Mining Conference held at the Rockefeller Foundation’s Bellagio Study and Conference Centre on Lake Como in Italy (22-26 July 1996), the organizers made a call to stud-ying extinct and extant mining and metallurgical communities as a social phe-nomenon (Knapp et al., 1998). Clearly, these repeated calls over the years un-derscore the potential of ethnographic approaches in unravelling such issues as the social context of production, gender, power strategies and labour ex-ploitation, imperialism and colonialism (Knapp, 1998). None of these themes, could be dealt with in the traditional studies of ancient technologies, which focused explicitly on the technical aspects of production, as pointed out by Dobres (2000). This underscores the appropriateness of ethnography for the current study.

When used with appropriate sampling for interviewees and skillful probing during oral interviews, ethnographic studies have the potential to bring out a multi-vocal perspective and deep-seated attitudes, beliefs and values embed-ded in the social practices of a society. A typical example is the study of iron working in southern and western Uganda by Dr. Louise Iles where a chance interview with a female respondent revealed that women were deeply involved in iron production, a dimension that male respondents never highlighted in earlier interviews (Iles, 2016). In the end, Iles, echoing the call by Schmidt (1998) and Arthur (2010) invited researchers to look beyond one gender as an agent of technology in order to reach and discuss its social constitution. This way of research has the potential to yield alternative and more socially nu-anced insights into past and present crafts production in Africa. Recurrently, focus has been laid on the male gender during interviews on precolonial tech-nologies of Africa (see Killick, 1990; Mapunda, 1995). Unfortunately, this has entrenched the stereotype of women as technologically naïve.

3.1.1 Direct observations and interviews Inspired by the above reviewed debates and studies, for this study, I chose to carry out detailed observations and interviews of a female smith living near the prehistoric urban centre of Great Zimbabwe, who has been conducting in-dependently organized forging and casting of scrap metals with her family members since the 1950s. Together with my research assistant, Yananiso Maposa, we recorded video clips of Mrs Kohliwe Zanhi, popularly known as Mbuya (grandma) Murozvi, forging a ceremonial hand axe (humbwa) besides a smithing hearth (chido) with the help of one of her grandsons. We also cap-tured more video clips and photographs of the female smith and one of her sons forging a hoe (badza), and her daughter-in-law carving a wooden handle (mupinyi) for the hoe. It is important to highlight that prior to interviewing the elderly artisan, we sought permission from the Chief himself, who sanctions such researches in his communal area. We also conducted interviews with

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male and female members of Chief Charumbira communal area aiming to es-tablish their attitudes towards Mbuya Murozvi and her family, who also is a renowned potter and producer of snuffing tobacco among several other crafts. Paper I is dedicated to the complexities and ambiguities of gender within a field of technology traditionally associated with males and a rural context con-ventionally viewed as rigidly hierarchical, where men top the ladder of power and creativity. In my future researches on gender and technology, I intend to include women in other technologies together with their male competitors to explore how the masculine and feminine aspects of our being human contrib-ute to power, knowledge and technology.

Eyewitness accounts of iron production activities recorded by European visitors to Sub-Saharan Africa before and during the colonial period remain a critical source of valuable information to archaeologists (e.g. Chirikure, 2006; Killick, 1990; Mapunda, 1995). Unfortunately, there is a dearth of written rec-ords for much of the earlier technological history of Great Zimbabwe up to the 19th century AD. Only a few written accounts exist covering the second half of the 19th century AD (Bent, 1892; Burke and Mauch, 1969). Although few, these records illuminate important aspects of the operational chain of iron production in the form quarrying of the iron ore, roasting, crushing, reduction, labor, furnace types, decorations as well as ritual performances during the smelt. I provide more information about their observations under the results sections in Chapter 4 and in Paper I.

3.2 Archaeology As illustrated in the foregoing sections, ethnographic sources and written rec-ords are important in adding layers of understanding to the archaeological data. However, the archaeological source material itself has been key in con-structing a better understanding of the technological skills and innovation in Zimbabwe and beyond. The archaeological data used in this thesis include both studies of pre-existing collections, surveys and archaeometallurgical analyses. In addition, wood charcoal analysis has been commissioned on ma-terial from archaeological sites. I explain the different archaeological ap-proaches used and methods employed in detail below.

3.2.1 Legacy Collections The Great Zimbabwe Conservation and Research Centre holds a fair amount of archaeometallurgical materials on its storerooms, recovered from sponta-neous surveys and excavations within and around the urban centre by previous researchers (e.g. Ndoro, 1994). In the planning phase, I examined these as-semblages to establish their value as sources of archaeological explanation.

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This also involved searching for the field reports generated during the respec-tive surveys and excavations. Unfortunately, I could not find any excavation notes. Although this makes working with legacy data a bit difficult, Bandama et al. (2017) profitably reconstructed aspects of Great Zimbabwe’s metallur-gical crucibles using such data. In my case, I found the details captured in the accessions register, excavation photographs and site index cards quite useful in building up background information to the collection in question, but also in planning the fieldwork. Discussions with researchers as Dr. Webber Ndoro and Prof Paul Sinclair who previously worked in and around Great Zimbabwe (see chapter 2.2) were important, in particular Sinclair’s participation in two of my field reconnaissance surveys.

3.2.2 Community Archaeology: a brief note In African Archaeology, there is an ever-growing call to produce knowledge in collaboration with local communities as a way of decolonizing archaeolog-ical and heritage management practice (Chirikure et al., 2008; Pikirayi and Schmidt, 2016; Pikirayi, 2016). Within this approach, archaeologists are viewed as co-producers rather than leaders of archaeological projects through sharing resources, decision-making and knowledge with members of local communities. Inspired by this approach, I introduced my study to various local leaders including Chief Fortune Charumbira and to his council of village heads at the communal court. Because of this rapport, local leaders took it upon themselves to introduce the project to their respective villagers, encour-aging people to report archaeometallurgical remains they frequently encounter in their maize fields. Apart from opening up for ethnographic surveys already discussed in section 3.1.1., the collaboration also assisted in identification of new archaeometallurgical sites. This introduction led to a series of more dis-cussions at some of the known iron production sites, where samples of the research materials were exhibited and explained. I also gathered invaluable information regarding transportation of iron ores and wood.

3.2.3 Archaeological field surveys Archaeological field surveys are not just a step towards excavations. They are also a means to answering archaeological questions regarding the physical and social use of the landscape (e.g. Pwiti, 1996; see also McIntosh, 2005; Wright, 2010 for urban landscapes). So far, archaeologists are still unclear about the source of Great Zimbabwe’s iron, doubting if there are iron production sites in the hinterland supplying the centre with metals (e.g. Bandama et al., 2016; Chirikure, 2015; Chirikure et al., 2017). Thus, I set out from the beginning of the PhD study to survey and record iron production sites in order to illuminate the presence and analyze shifting distributions and concentrations of iron working activities over time in areas.

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The field surveys were conducted from October 2013 before the onset of the rainy season when visibility of archaeological materials on the ground is at its best. However, the surveys skirted the Mutirikwi Recreational Park im-mediately to the north as the Parks and Wildlife Management Authority did not grant a research permit. The Great Zimbabwe’s mosaic landscape was di-vided into four broadly defined landforms: river valleys, cultivable land, whale-backed hills and stand-alone granite features such as bornhardts, castle kopjes and tors. These units were subjected to intensive foot surveys by a team of seven participants (including three archaeology students from the Great Zimbabwe University who were on attachment at the Great Zimbabwe World Heritage Site, two local committee members, one curator of archaeology and a surveyor from the National Museums and Monuments of Zimbabwe). Scat-ters of slags, tuyere fragments, broken furnace rubble and iron-ore quarry sites were documented using a GPS and camera. The range of materials was rec-orded to tease out the various technologies practiced at the site and their social settings (Chirikure, 2005; Killick, 1990). Samples of beads, pottery, and a clay figurine were collected for further analysis and curation at the GZCRC (see summary table of sites and finds in Table 1).

3.2.4 Archaeological excavations Owing to constraints of time and funds, I prioritized sites exhibiting poorly understood technologies such as large concentrations of multiple-fused tuy-eres, slags and possible furnace for excavations as shown in the next section. Thus, I conducted excavations at three different sites in the wider cultural landscape of Great Zimbabwe namely, Boroma, Veza 1 and Mutevedzi. In addition, I have also included material from Mashava, which I excavated in 2010; Goose Bay, excavated by David Collett in 1986; and Chigaramboni, excavated by Webber Ndoro in 1991. Below are the descriptions of the ar-chaeological excavations, including some brief notes about the sites under in-vestigation (see Table 1).

3.2.4.1 Boroma Site Boroma site lies approximately four kilometres northeast of Great Zimbabwe World Heritage Site, making it one of the iron working sites closest to the urban centre. Intra-site surveys at Boroma site identified two distinct activity areas – an iron smelting and smithing locations, the latter in association house foundations. Broken furnace rubble, slags and tuyeres occurred at the foot of granite boulders nearest to Chebopopo stream and numerous natural springs. The natural springs in this area, which were recorded during a survey of Great Zimbabwe’s water resources (see Pikirayi et al., 2016), are key to agricultural and domestic usage of water, and would have been exploited for iron produc-tion activities in the past. Remains of iron smithing activities, in the form of a possible smithing hearth, slags, and flat surfaced granite blocks, were located

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less than 200m further west of the smelting activity area on a low-lying granite rock outcrop where run-off continues to erode away artifacts. Isolated domes-tic artifacts such as a piece of green and white chinaware, a potsherd with cross hatched lines and an iron hoe blade were collected from the cultivated land between the smelting and smithing areas. These were too few to shed adequate light towards our understanding of the period of occupation and the contemporaneity of the settlement and the iron working activities.

Three 2 x 2 m trenches were excavated at Boroma site in order to locate furnace remains. Trench 1 was located in an area of dense scatter of tuyeres and furnace rubble in supposedly less disturbed eastern edges of cultivated land. The trench was excavated to a depth of 20 cm when a hut floor was found, no archaeological materials from this trench and it was therefore aban-doned.

Trench 2 was located right at the foot of one of huge boulders that bordered the eastern edges of the cultivated piece of land where there was the densest scatter of broken tuyere, furnace rubble and blocks of slag. The trench was excavated in spits to a depth of about 60 cm depth (Figure 3). The soil was sieved using a 4x4 mm sieve. The first spit (0-10 cm), which was largely made up of humus, contained a mixture of tuyeres, slags and furnace rubble. Dark-brown soil and a dense mixture of furnace rubble, multiple fused and single tuyeres, and a few fragments of furnace slags characterized the second spit (10-20 cm). The eastern end of the trench yielded a charcoal bed from which samples were collected for both radiocarbon dating and tree species identifi-cation. The third spit (20-40cm), a continuation of the dark brown soils from the second spit, yielded more tuyeres, and slags with plant impressions. Below this layer was a reddish brown layer which yielded some roots and stones after which was a sterile layer.

The third trench enclosed a possible smithing hearth on top of a low-lying granite whaleback, locally known as ruware, which borders the western edge of the piece of cultivated land between the two iron working areas. Because of the shallow soil, Trench 3 was excavated to a depth barely 10 cm before reaching the surface of the rock outcrop. The structure measures about 100cm in diameter, with an average wall thickness of 10cm and a depth of 15cm.The ground immediately outside the structure seemed plastered and pole im-pressed mud, dhaka, was scattered around, which suggests that the hearth had a possible shelter around it. The trench yielded undiagnostic potsherds and few pieces of slag. At least three house foundations were identified on the same rock outcrop next to the smithing hearth, illustrating the complexity and ambiguity of technological organization in African iron metallurgy.

The excavations at Boroma Site recovered iron slag, broken tuyere pieces, furnace rubble, and charcoals. The bulk of slag from Trench was made up of large cake like blocks, the largest one measured about 15 x 13 cm, and a thick-ness of about 7 cm, suggesting that these were furnace slag. Some of these blocks had plant impressions and possible bone inclusions. Trench 3 yielded

39

small slag pieces of amorphous shape measuring 3 x 2 cm on average. The slag had very low magnetism and was very porous. At least 30 broken tuyere pieces measuring at most 15 cm in length were recovered from Trench 2. A maximum of four broken tuyere pieces were found fused together, suggesting that the smelting process used natural draft air supply mechanism. Both single and multiple-fused tuyere exhibited evidence of vitrification and collapse at the distal end, indicating that these were inserted deep into the furnace where they were affected by very high temperatures. The internal diameter of the different tuyeres recovered at Boroma site ranged between 30 and 40 cm, while their external diameter measured between 50 and 60cm.

Figure 5. Boroma Site, Trench 2 West Facing Wall.

3.2.4.2 Veza A site The Veza 1 iron working site is located about 8 km south-west of Great Zim-babwe. It is situated at the foot of the western slope of a large granite inselberg and is bounded on the south by the Veza River about 100 metres away, which would have supplied water for the iron production activities at the site. Right within the site is an abandoned modern homestead whose flowerbeds and courtyard were demarcated using blocks of finger-impressed and vitrified fur-nace rubble. Members of the abandoned homestead also heaped blocks of iron slag (measuring approximately 20 x 15 cm) together with granite stones on the family graves located on the western side of the site. Other blocks of slags, furnace rubble and pieces of tuyere were cleared from the land surrounding the homestead in preparation for maize cultivation and made into large heaps on the edges of the fields. Foot surveys around the site identified more iron production debris towards the top of the granite inselberg about 800 m east of the main site. The site has a striking density of very small sizes of iron slag that spreads out over an area of about 3 hectares.

Humus

Dark brown soil

Reddish brown soil

Sterile layer

Tuyere

Roots

Stones

0 20 40cm20

40

A 2 x 2 m trench was located at the centre of the homestead where a con-centration of broken tuyeres, slag pieces and blocks of furnace rubble was noticed protruding from the ground and being partially exposed by soil ero-sion. The homestead area was expected to produce high quality material for dating and archaeometallurgical analyses as compared to the rest of the site, which was disturbed from years of ploughing. The trench was excavated by a combination of arbitrary spits and natural stratigraphy to a depth of 40 cm. The first layer, an arbitrary spit of 10 cm, exposed more broken tuyere pieces clustered together with amorphous slag pieces and vitrified blocks of furnace rubble than were visible on the surface. Its soil, composed by gritty earth or gravel, was compacted. The second layer, about 10 – 30 cm thick, yielded much more of the same archaeometallurgical materials than those excavated in the first spit. In addition, there were charcoal fragments within the the clus-ter of tuyeres and slag pieces. These iron production debris rested on the vit-rified floor a possible furnace pit, which dipped slightly westwards (Figure 6; see also Paper 1, Figure 7). The final layer, about 10 cm, was entirely gritty earth and sterile.

Figure 6. The floor plan of Level 3 and north facing wall of the excavation trench at Veza A site.

3.2.4.3 Mutevedzi site Mutevedzi site is located 6km south-west of Great Zimbabwe World Heritage Site. The site is located on a pass where two hills, one on the east and the other on the west, flanked the iron working location. A perennial stream, Shambinyara, flows past the site some 200m away to the north, which would have supplied water for the iron working activities at the site. A dense scatter of slag, tuyere fragments and furnace rubble spread across an area covering 3 hectares. A thriving business centre was established within the boundaries of

Furnace wallTuyeresStone

0 40 80cm20

Key

Tuyere fragment

Broken furnace wall

Brown soil

Reddish brown soilHumus

Sterile layer

Charcoal

Slag

0 4020

Key

80cm

41

this site, destroying some of the archaeometallurgical heritage during the con-struction of retail stores of Mutevedzi Business Centre, also known as Nez-vigaro.

A large trench measuring 5 m x 3 m was situated between two shop build-ings surrounding a cluster of at least twenty tuyeres tuyeres partially exposed by years soil of erosion (Figure 7, top right of photo). The trench was exca-vated by a combination of arbitrary spits and natural stratigraphy to a depth of about 50cm. The first excavation spit was an arbitrary spit about 10 cm thick, which was made up of layers of very dark reddish brown, dark reddish brown and dull reddish brown soils (see profile in Figure 7). Thick tree roots had grown into and in between some of the tuyeres clustered in this layer, breaking them apart over the years. The second layer had reddish brown, a continuation from layer one. It yielded more tuyeres, some of which fused in multiples in association with a rectangular furnace base. The furnace wall, which was about 15 cm thick, had visible finger impressions, vitrification, and evidence of a possible leakage of slag through the wall. The floor of the furnace sloped gently northwards and the southern end of the furnace was destroyed. The furnace base, which measured about 2 x 1 showed evidence of slag leakage through the cracks in its 10 cm thick wall. The rectangular furnace base is a unique design discovered at Mutevedzi site. It is unclear whether this furnace was once similar to the one described under Veza A above. Underneath this layer, the soil turned dark red and there were no more traces of cultural mate-rials.

42

Figure 7. Mutevedzi trench stratigraphy (top). Rectangular shaped furnace base (bottom). Here note the cluster of tuyeres at the top right corner of the photograph.

Tuyere fragment

Broken furnace rubble

Very dark reddish brown soil

Dark reddish brown soil

Dull reddish brown soil

Reddish brown soil

Dark red soilTree root

0 40 80cm20

Key

43

Tab

le 1

. Iro

n pr

oduc

tion

site

s in

the

wid

er a

rcha

eolo

gica

l lan

dsca

pe o

f G

reat

Zim

babw

e. T

he g

rey

shad

e re

pres

ents

exc

avat

ed s

ites.

Loc

al S

ite

Nam

e G

eogr

aphi

cal

Res

earc

hers

C

oord

inat

es

Mat

eria

ls D

escr

ipti

on

Con

text

of

Loc

atio

n

Ori

enta

tion

Sit

e N

atur

e of

Tec

hno-

logy

Mas

hava

20

° 03

' 54,

00''

S 30

° 31

' 46,

00''

E

Mte

twa,

E

.

Furn

ace

rubb

le, i

ron

ore,

fl

ow a

nd f

urna

ce s

lags

, fu

sed

and

sing

le tu

yere

s

Iron

-ore

fie

lds,

w

oodl

ands

, no

sett

le-

men

ts, s

trea

m

Wes

t sid

e of

hill

wit

h ir

on-o

re q

uarr

y on

the

east

sid

e of

hil

l

Nat

ural

dra

ft

Bor

oma

20°

16' 0

2,14

'' S

30°

58' 0

0,30

'' E

M

tetw

a,

E.

Furn

ace

rubb

le, s

lag

wit

h bo

ne in

clus

ions

, sm

ithi

ng

slag

, fus

ed a

nd s

ingl

e, ir

on

hoe.

Woo

dlan

ds, n

ear

vil-

lage

and

str

eam

. W

est s

ide

of g

rani

te

boul

ders

N

atur

al d

raft

Mor

gens

ter

Roa

d 20

° 17

' 01,

60''

S 30

° 55

' 51,

50''

E

Mte

twa,

E

.

Chu

nky

slag

and

tuye

re

frag

men

ts

Woo

dlan

ds, n

ear

pe-

renn

ial s

trea

m

Wes

t of

gran

ite

boul

-de

rs

For

ced

draf

t

Muk

ungw

a 1

20°

16' 4

7,60

'' S

30°

56' 3

5,00

'' E

M

tetw

a,

E.

Chu

nky

iron

sm

elti

ng s

lag,

fu

rnac

e ru

bble

, tuy

ere

frag

men

ts

Woo

dlan

ds, p

eren

-ni

al n

atur

al s

prin

g,

mar

shes

Wes

t of

gran

ite

boul

-de

rs

For

ced

draf

t

Muk

ungw

a 2

20°

17' 0

0,00

'' S

30°

56' 1

9,30

'' E

M

tetw

a,

E.

Furn

ace

slag

and

tuye

re

frag

men

ts

Woo

dlan

ds a

nd

mar

shes

W

est o

f gr

anit

e bo

ul-

ders

F

orce

d dr

aft

Muk

ungw

a 3

20°

16' 5

5,00

'' S

30°

56' 2

4,80

'' E

M

tetw

a,

E.

Tap

and

fur

nace

sla

g W

oodl

ands

and

st

ream

s W

est o

f gr

anit

e bo

ul-

ders

F

orce

d dr

aft

Nem

anw

a G

P

20°

16' 2

0,50

'' S

30°

54' 5

0,80

'' E

M

tetw

a,

E.

Slag

sca

tter

s an

d tu

yere

fr

agm

ents

W

oodl

ands

W

est o

f gr

anit

e bo

ul-

ders

U

ncer

tain

Vez

a A

20

° 17

' 46,

60''

S 30

° 50

' 29,

90''

E

Mte

twa,

E

.

Bul

ky v

itri

fied

fur

nace

ru

bble

, mul

tipl

e fu

sed

&

sing

le tu

yere

s

Woo

dlan

ds, i

ron-

ore

fiel

ds, p

eren

nial

st

ream

Wes

t of

gran

ite

wha

le-

back

, wes

t-fa

cing

es-

carp

men

t

Nat

ural

dra

ft

44

Vez

a B

20

° 18

' 20,

40''

S 30

° 50

' 19,

90''

E

Mte

twa,

E

.

Bul

ky v

itri

fied

fur

nace

w

alls

, mul

tipl

e fu

sed

&

sing

le tu

yere

s

Woo

dlan

ds, i

ron-

ore

fiel

ds, p

eren

nial

st

ream

Wes

t of

gran

ite

boul

-de

rs

Nat

ural

dra

ft

Goo

se B

ay

20°

13' 5

3,65

'' S

30°5

9' 4

1,28

'' E

C

olle

tt, D

. P.

M

tetw

a,

E.

Sin

gle

tuye

res,

pha

llic

ob-

ject

, cru

cibl

e, h

ouse

flo

or,

deco

rate

d po

tter

y

Woo

dlan

ds, p

eren

-ni

al r

iver

, wit

hin

set-

tlem

ent

Wes

t of

gran

ite

boul

-de

rs

For

ced

draf

t

Gre

at Z

imba

bwe

1 20

° 16

' 03,

18''

S 30

° 56

' 04,

52''

E

Ban

dam

a et

al.

Mte

twa,

E

.

Sla

g sc

atte

rs

Wit

hin

the

Hill

Com

-pl

ex

Sur

roun

ded

by g

rani

te

boul

ders

all

-rou

nd

Unc

erta

in

Gre

at Z

imba

bwe

2 20

° 15

' 54,

07''

S 30

° 56

' 04,

52''

E

Ban

dam

a et

al.

Mte

twa,

E

.

Slag

sca

tter

s N

ear

the

Eas

tern

En-

clos

ure

Wes

t of

gran

ite

boul

-de

rs

Unc

erta

in

Gre

at Z

imba

bwe

3 20

° 16

' 02,

68''

S 30

° 56

' 04,

52''

E

Ban

dam

a et

al.

Mte

twa,

E

.

Slag

sca

tter

s N

ear

the

Eas

tern

En-

clos

ure

Wes

t of

gran

ite

boul

-de

rs

Unc

erta

in

Gre

at Z

imba

bwe

4 20

° 16

' 11,

39''

S 30

° 55

' 58,

44''

E

Ban

dam

a et

al.

Mte

twa,

E

.

Slag

sca

tter

s T

erra

ced

Hil

l E

ast o

f Si

te M

useu

m

Hil

l U

ncer

tain

Gre

at Z

imba

bwe

5 20

° 15

' 40,

00''

S 30

° 55

' 43,

25''

E

Ban

dam

a et

al.

Mte

twa,

E

.

Sla

g sc

atte

rs

Ope

n sp

ace

On

top

of w

hale

back

hi

ll U

ncer

tain

Gre

at Z

imba

bwe

6 20

° 15

' 29,

60''

S 30

° 55

' 59,

80''

E

Mte

twa,

E

Sla

g w

ith

bone

incl

usio

n W

oodl

ands

and

pe-

renn

ial s

trea

m

Wes

t of

anth

ill

Unc

erta

in

45

Mut

eved

zi B

.C.

20°

18' 1

3,30

'' S

30°

52' 5

0,00

'' E

M

tetw

a,

E.

Clu

ster

of

fuse

d an

d si

ngle

tu

yere

s, f

urna

ce r

ubbl

e,

slag

wit

h gr

ass

impr

essi

ons

Woo

dlan

ds, p

eren

-ni

al s

trea

m,

Nar

row

gap

in b

etw

een

two

gran

ite

hill

s N

atur

al d

raft

Nez

viga

ro

20°

18' 1

6,10

'' S

30°

52' 5

0,00

'' E

M

tetw

a,

E.

Clu

ster

of

fuse

d an

d si

ngle

tu

yere

s, f

urna

ce r

ubbl

e,

slag

wit

h gr

ass

impr

essi

ons

Woo

dlan

ds, i

ron-

ore

fiel

ds, p

eren

nial

st

ream

Wes

t of

gran

ite

boul

-de

rs

Nat

ural

dra

ft

Chi

kwir

a 1

20

° 19

' 55,

02''

S 30

°47'

16,

08''

E

Mte

twa,

E

. F

used

tuye

res,

fur

nace

rub

-bl

e, s

lags

W

oodl

ands

, iro

n-or

e fi

elds

, in

the

hill

s W

est o

f gr

anit

e bo

ul-

ders

N

atur

al d

raft

Chi

kwir

a 2

20°

20' 0

7,08

'' S

30°

47' 2

4,78

'' E

M

tetw

a,

E.

Furn

ace

rubb

le, f

used

and

si

ngle

tuye

res,

cir

cula

r fu

r-na

ce b

ases

Woo

dlan

ds, i

ron-

ore

fiel

ds, i

n th

e hi

lls

Wes

t of

gran

ite

wha

le-

back

N

atur

al d

raft

Chi

gara

mbo

ni 1

20

° 18

' 30,

46''

S 30

° 28

' 11,

68''

E

Ndo

ro, W

. M

tetw

a,

E.

Furn

ace

rubb

le, f

used

&

sing

le tu

yere

s, c

hunk

s of

sl

ag

Woo

dlan

ds, i

ron-

ore

fiel

ds, w

ater

-cou

rse

Wes

tern

edg

e of

hil

l N

atur

al d

raft

Chi

gara

mbo

ni 2

20

° 20

' 53,

02''

S 30

° 46

' 06,

06''

E

Ndo

ro, W

. M

tetw

a, E

F

urna

ce b

ases

, rub

ble,

sl

ag, f

used

and

sin

gle

tuy-

eres

Woo

dlan

ds, i

ron-

ore

fiel

ds, w

ater

-cou

rse

Wes

t sid

e of

hil

l N

atur

al d

raft

Chi

gara

mbo

ni 3

20

° 20

' 30,

30''

S 30

° 46

' 30,

94''

E

Ndo

ro, W

. M

tetw

a, E

Fu

rnac

e ru

bble

, sla

g, f

used

an

d si

ngle

tuye

res

Woo

dlan

ds, i

ron-

ore

fiel

ds

Wes

tern

edg

e of

hil

l N

atur

al d

raft

Chi

gara

mbo

ni 4

20

° 19

' 56,

03''

S 30

° 46

' 23,

52''

E

Ndo

ro, W

. M

tetw

a, E

Fu

rnac

e ru

bble

, sla

g, s

in-

gle

tuye

res

Woo

dlan

d, I

ron-

ore

fiel

ds, w

ater

-cou

rse

Ope

n fi

eld

Forc

ed d

raft

Chi

gara

mbo

ni 5

20

° 20

' 24,

14''

S 30

° 46

' 44,

47''

E

Ndo

ro, W

. M

tetw

a, E

S

ingl

e tu

yere

fra

gmen

ts

and

slag

W

oodl

ands

, iro

n-or

e fi

elds

O

pen

fiel

d Fo

rced

dra

ft

Chi

gara

mbo

ni 6

20

° 20

' 12,

70''

S 30

° 46

' 54,

34''

E

Ndo

ro, W

. M

tetw

a, E

F

used

tuye

re f

ragm

ents

an

d sl

ag

Woo

dlan

ds, i

ron-

ore

fiel

ds

Wes

t and

at t

he f

oot o

f hi

ll o

verl

ooki

ng s

trea

m

Nat

ural

dra

ft

Chi

gara

mbo

ni 7

20

° 19

' 50,

56''

S 30

° 46

' 58,

40''

E

Ndo

ro, W

. M

tetw

a, E

F

urna

ce b

ases

, rub

ble,

sl

ag, f

used

and

sin

gle

tuy-

eres

Woo

dlan

ds, i

ron-

ore

fiel

ds

Wes

tern

edg

e of

hil

l N

atur

al d

raft

46

Chi

gara

mbo

ni 8

20

° 19

' 56,

57''

S 30

° 49

' 27,

78''

E

Ndo

ro, W

. M

tetw

a, E

F

urna

ce b

ases

, rub

ble,

sl

ag, f

used

and

sin

gle

tuy-

eres

Woo

dlan

ds, i

ron-

ore

fiel

ds

Wes

tern

edg

e of

hil

l N

atur

al d

raft

Chi

gara

mbo

ni 9

20

° 02

' 06,

94''

S 30

° 47

' 44,

12''

E

Ndo

ro, W

. M

tetw

a, E

F

urna

ce b

ases

, rub

ble,

sl

ag, f

used

and

sin

gle

tuy-

eres

Woo

dlan

ds, i

ron-

ore,

w

ater

-cou

rse

W

este

rn e

dge

of h

ill

Nat

ural

dra

ft

Chi

gara

mbo

ni 1

0 20

° 20

' 00,

56''

S 30

° 47

' 44,

12''

E

Ndo

ro, W

. M

tetw

a, E

F

urna

ce b

ases

, rub

ble,

sl

ag, f

used

and

sin

gle

tuy-

eres

Woo

dlan

ds, i

ron-

ore,

pe

renn

ial s

trea

m

Wes

t sid

e of

hil

l N

atur

al d

raft

Chi

gara

mbo

ni 1

1 20

° 19

' 50,

59''

S 30

° 47

' 43,

48''

E

Ndo

ro, W

. M

tetw

a, E

F

urna

ce b

ases

, rub

ble,

sl

ag, f

used

and

sin

gle

tuy-

eres

Woo

dlan

ds a

nd

mar

shes

W

este

rn e

dge

of h

ill

Nat

ural

dra

ft

Chi

gara

mbo

ni 1

2 20

° 20

' 01,

18''

S 30

° 47

' 55,

10''

E

Mte

twa,

E

. F

urna

ce b

ases

, rub

ble,

sl

ags,

fus

ed a

nd s

ingl

e tu

y-er

es

Woo

dlan

ds a

nd

mar

shes

W

este

rn e

dge

of h

ill

Nat

ural

dra

ft

Chi

gara

mbo

ni 1

3 20

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48

3.3 Archaeometallurgy Archaeometallurgy combines materials science, social archaeology and mate-rial culture studies to answer archaeological questions regarding the produc-tion and use of metals in past societies (Buchwald, 2005; Chirikure 2015; Killick and Fenn, 2012; Pleiner, 2000; Rehren, 2000; Roberts and Thornton, 2014). Archaeometallurgical methods may give information on technological choices, opportunities and constraints (Chirikure 2005, Rehren et al. 2007). The study is based on selected iron production debris such as slags, tuyere fragments, pieces of bloom and possible iron ores recovered from the areas surrounding the Great Zimbabwe urban centre. Below I summarize the mate-rials and methods adopted in this study.

3.3.1 Visual and Macroscopic observations The first level of archaeometallurgical analyses involved the visual and mac-roscopic examination of furnace blocks, tuyere pieces, varied types of slags, possible mineral ores and piece of iron bloom (e.g. Bayley et al 2001; Chiri-kure 2005; Greenfield and Miller 2004; Mapunda 1995). I used a physical attributes analysis schedule developed by Bertram Mapunda (1995), which enabled the initial classification of materials and interpretation of metallurgi-cal processes as outlined in detail in Paper III. Much of this type of analysis was conducted in the field where such features as furnaces, large numbers of tuyeres and heaps of slags were examined in situ and reburied for further re-search.

3.3.2 Microscopic and chemical analyses of slags and piece of iron bloom

The second level of analysis involving laboratory techniques focused on the chemistry and microstructure of slags. The selected slag samples were ex-ported to Sweden for examination at the Geoarkeologiska Laboratorium (GAL) Uppsala, where I also received training in archaeometallurgy. Some of the samples were sent to Axinit in Bratislava, Slovakia, for the production of polished thin sections and the microstructure was analysed using optical mi-croscopy. Major chemical and trace elements were measured in 14 iron slag samples using ICP-AES and ICP-MS (see Paper IV for more details). Identi-fication of mineralogical phases present in the analyzed slags was carried out on the polished thin sections. I used a Zeiss Axioskop 40A polarization mi-croscope (up to 500x) to view the polished sections for slags at the GAL.

A possible piece of iron bloom was sectioned and polished for metallo-graphic analysis at the GAL. This involved grinding the sample on a polishing machine using silicon carbide papers (120-1200 grit) first before a 1μm finish using a Diaduo paste. The microstructure of the sample was analysed under a

49

Zeiss Axioskop 40A polarization microscope at magnifications up to 500x equipped with an integrated digital camera (Zeiss AxioCam MRc5). Determi-nation of the type of iron involved etching the polished block using 2% nitric acid in alcohol and examining it under the microscope for the detection of carbon. The amount of carbon present in a sample is what determines whether a piece of metal is cast iron, steel or wrought iron.

3.4 Archaeometry of metallurgical ceramics Archaeometry, as a science-based subdiscipline of archaeology, is primarily concerned with the physical and mechanical properties of material culture (Jones, 2004). It employs chemistry, physics and geology to address how peo-ple made, exchanged, used and discarded artefacts (e.g. Bandama et al., 2017; Tite, 2008). Tuyeres from varied sites around Great Zimbabwe were exam-ined, as they are a rich resource for understanding specialized production of metallurgical ceramics in the past. Macroscopic attributes of tuyeres recovered from varied sites in Great Zimbabwe were examined based on shape, which is often diagnostic of the air supply mechanisms used to drive the iron smelting furnaces. In African iron metallurgy, tuyere form is also important as some are shaped to look like parts of the male reproductive organs, providing a win-dow into understanding broader cultural values embedded in technology (e.g. Chirikure et al., 2009; Schmidt, 2009). A detailed study of selected tuyeres was carried out (see Paper V) and summarized below.

3.4.1 Materials and methods The tuyeres materials subjected to laboratory analyses in this study were se-lected from the sites shown in Table 1 below.

50

Table 2. Tuyere materials from iron production sites around Great Zimbabwe sub-jected to archaeometrical analyses

Site Name Sample ID

Sample Con-text

Thermal & Sur-face Condition

Color

Boroma BOA1 Part of a single tuyere from in-side furnace

Vitrified and free of slag traces

Greyish brown

Boroma BOA2 Multiple fused Vitrified and free of slag traces

Brick red

Mutevedzi MUI1 Part of tuyere fused in multi-ples

No trace of slag Reddish yellow

Mutevedzi MUI2 A different tuy-ere fused with MUI1

2 mm layer of slag on the outside sur-face

Reddish yellow

Veza A VEA1 Double fused tuyeres

Vitrified with droplets of slag on the external sur-face

Dark grey-ish brown

Veza B VEA2 Double fused tuyeres

Extensively coated on the distal end

Reddish brown

Chigaram-boni

CHI1 Part of tuyere fused in multi-ples

Vitrified and free of slag traces

Greyish brown

Chigaram-boni

CHI2 Different part but same tuyere as CHI1

Vitrified and free of slag traces

Greyish brown

3.4.1.1 X-Ray Fluorescence A Thermo Scientific portable (handheld) XRF analyser (h-XRF, Niton XL3t 970 GOLDD+), was used to measure X-ray fluorescence (XRF) on a freshly cut cross-section on slightly polished samples (see Paper V for details). The XRF method has highly accurate determinations for elements (Helfert & Böhme 2010; Helfert et al. 2011; Papmehl-Dufay et al. 2013), and is a non-destructive method. The analysis included the elements: Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Ba, W, Au, Pb, Bi, Th and U. Elements in the range from Sodium (Na) and lighter cannot be detected by this method. Analyses were performed on a freshly made cut on the cross section of the sherds.

3.4.1.2 Petrographic microscopy Thin sections of 0.03 mm thickness were prepared. The coarseness of the paste, the amount of coarse silt, fine sand, medium sand, coarse sand and fine

51

gravel (ISO 14688-1:2002) was calculated under a polarising microscope us-ing Nikon NIS Elements Br Imaging Software (ver. 3.10). The mineralogy of the sand fraction was determined through standard petrographic procedures.

3.4.1.3 Thermal analyses The thermal properties of clays vary according to their composition, i.e. the type of clay minerals in question, the presence of oxyhydroxides of iron, cal-cite, fluxing ions (Na, K, ca and Mg), amount of primary quartz and feldspar, coarse fraction etc. In order to study the variations in the thermal properties, analyses by means of the Thermal Colour Test (TCT) and the sintering interval have been performed (Hulthén 1976, Lindahl 1985). Statistical calculations were performed using IBM SPSS Ver.24.

3.5 Archaeobotany – an anthracological approach Wood resources are crucial in iron technology both for technological innova-tion and also varied ritual and social contexts (Iles, 2016; Lyaya, 2013; Mapunda, 2010). The appropriation of wood for metallurgical purposes in Great Zimbabwe is thought, by some, to have caused significant deterioration of the environment, contributing to its eventual collapse among other socio-political factors (Bannerman, 1982; Chikumbirike, 2014; Pikirayi, 2006). The dearth of a detailed vegetation history of the Great Zimbabwe area, has limited possibilities of both testing the degradation hypothesis and/or exploring wood selection and management in relation to iron technology. As part of the PhD project, I therefore undertook to explore possible selection and outtake of wood species for metallurgical purposes through woodcharcoal analyses. The method has been successfully applied in the reconstruction of the vegetation history and paleoclimates of some locations in South Africa such as Colwin-ton, Banowe and Ravenscraig (Tusenius, 1986), as well as for instance Boom-plaas (Scholtz, 1986). Charcoal analyses has also been used for landscape re-construction in southern Africa (February, E., & Van der Merwe 1992; Deacon et al 1983; Ekblom et al. 2014; Esterhuysen, A. B., & Mitchell 1996; Vogelsang, R., & Eichhorn 2011). In particular, anthracology has also been used to address iron metallurgy questions elsewhere in the continent (Schmidt 1994).

3.5.1 Material An assemblage of 108 charcoal fragments, which originated from proper ar-chaeological excavations at Boroma, Goose Bay and Veza 1 sites in the wider archaeological landscape of the Great Zimbabwe centre, were analyzed (Table 3). The charcoal samples were recovered through dry sieving.

52

Table 3. Archaeological charcoal from the Great Zimbabwe cultural landscape sub-jected to anthracological analysis

Site Name Location Context Collection Method

Collector Quantity

Boroma 20° 16' 02,14'' S 30° 58' 00,30'' E

Iron smelting site

Excavation Ezekia Mtetwa 2013

82

Goose Bay 20° 13' 53,65'' S 30° 59' 41,28'' E

Iron smelting site

Excavation David Coll-ett 1986

13

Veza 1 20° 17' 46,60'' S 30° 50' 29,90'' E

Iron smelting site

Excavation Ezekia Mtetwa 2014

33

TOTAL 108

3.5.2 Method Dr. Joseph Chikumbirike, of School of Humanities, Sol Plaatje University, Kimberley, South Africa and an affiliate of the University of the Witwaters-rand, School of Geography, Archaeology and Environmental Studies con-ducted the charcoal identification analysis. Charcoal fragments were manually snapped between the fingers into three different planes namely the transverse section (TS), the tangential longitudinal section (TLS) and radial longitudinal section (RLS). The specimens were identified using a Zeiss Stemi, high power Olympus BX51 petrographic microscope, and an Olympus SC30 camera with an Olympus Imaging Solutions Software for image analysis. The charcoal samples were analysed under a magnification of x50, x100 and x200. Wood identification was based on attributes as growth ring boundaries, wood poros-ity, vessels per square millimeter and parenchyma types. The type of rays (i.e. ray width, height, cellular composition, storied structure), fibres (septate fibre, fibres with simple pits), tracheids (vascular/vasicentric tracheids), and tyloses were used as a basis of identification.

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4 Results

In this chapter, I present the results of the different data collection methods adopted in the study to illuminate the nature of iron production technologies present in the wider archaeological landscape of Great Zimbabwe. Examples of these results are presented here to provide the material basis of the specific discussions covered in the respective publication articles. First, I present evi-dence of technological variability as gleaned from written records, legacy col-lections and recent archaeological field surveys and excavations. The second section presents results from laboratory techniques for analyzing iron slags, a piece of possible iron bloom and tuyeres. In the last section, I present results of anthracological analysis of charcoal samples recovered during excavation of iron production sites around Great Zimbabwe. In the next chapter, I give a discussion of these results, which I interpret within the social agency and ma-teriality theoretical frameworks.

4.1 Evidence from written records: smelting techniques, organization and ritual practices

The writings of both Carl Mauch and Theodore Bent, who visited the Great Zimbabwe area in the late 19th century AD, reveal that contemporary Shona communities made use of forced draft techniques to smelt iron in low shaft furnaces. Bellows made of goatskin were used to drive combustion air into the furnace through two openings at ground level, which according to Mauch, was sufficient to bring the ore to melting point (Burke and Mauch, 1969: 137). As a geologist, he also noted that the smelters exploited a chalk-slate containing ferruginous mica for iron ore, which they quarried from a local source, a walk of about 20 minutes. As part of thermal treatment, the smelters crushed the ores into small pieces before smelting them, a process they repeated over a period of between 5 to 8 days.

Apart from the drinking of beer to incentivize those pumping the bellows, Mauch did not report any ritual treatments of the furnaces because either he witnessed none, or the performances were there, but nothing worth recording. As reflected in Bent’s writings, ritual performances were a common phenom-enon in the indigenous iron metallurgy of many Shona subgroups in the late 19th and early 20th centuries AD (Bent, 1892), including many other societies

54

in Sub-Saharan Africa (Childs and Killick, 1993; Cline, 1937; Herbert, 1993; Schmidt, 2009; Terry Childs, 1991). I will deal with their implications in the discussion chapter in light of results from recent researches across the conti-nent. Mauch did not also provide direct information regarding the roles of men and women in iron production activities, but since the reported smelting epi-sode took outside the village, it is most likely that only men were present at the smelting site.

Another outcome from Mauch’s eyewitness account critical for this study are the archaeometallurgical remains he reported of an earlier type of iron technology in the form of broken furnace rubble and broken clay tuyeres fused in doubles. Both Mauch and the local residents regarded these remains as be-longing to an advanced iron technology, which they associated with an alleged white population that occupied the country in deep prehistory (Burke and Mauch, 1969: 136-137). Here the most important thing is that these remains indicate the presence of natural draft iron smelting technologies in the Great Zimbabwe area earlier on, contrasting sharply with the forced draft technology in use during Mauch’s time. The two assemblages represented significant technological changes in the same area over time.

Bent’s writings add more details to the results gleaned from Mauch’s report above. Bent noted that the Shona communities in Chivi, about 30km west of Great Zimbabwe, also used low shaft forced-draft iron smelting techniques in the 1890s. He also observed that the Chivi furnaces were designed as a woman giving birth, the chimney being the head decorated invariably with eyes, nose and mouth, and breasts (Bent, 1892). Importantly, he noted that the smelters carried out ritual performances and observed restrictive taboos against female participation in the iron production process. Interestingly, the types of fur-naces reported by the travelers have been corroborated by archaeological ex-cavations at different sites in the Great Zimbabwe area such as Gokomere Mission (Ndoro, 1994; Sinclair, 1984) and around Zimbabwe (Bernhard, 1962; Cooke, 1959; Chirikure, 2006, 2005; McCosh, 1979). According to Prendergast (1979; 1974), the low shaft forced draft furnace was the most common type used by the Shona in the 19th century.

4.2 Existing Collections The archaeometallurgical materials recovered in previous researches included three sites namely Goose Bay, Chigaramboni and Mashava. The funnel-shaped tuyere from Goose Bay suggest the use of forced-draft technol-ogy at the site. My examination of archaeometallurgical materials from Chi-garamboni (Figure 4) identified large blocks of furnace rubble, tuyeres fused in multiples, and large and dense slags. Field photographs also show a very dense cluster of tuyeres in the excavation trench (Figure 5).

55

My own rescue excavations at Mashava ironworking site in 2010 revealed iron production debris at the site including about twenty possible furnace fea-tures, massive and dense slag and heaps of tuyeres (Mtetwa, 2011). Some of the slag pieces at the site are tuyere-moulded (Figure 5), showing the cylindri-cal shape of the tuyeres into which the molten slag flowed and solidified. Other slag pieces show a clear flow texture in the form of wrinkled red-brown surfaces and sand impression underneath (see Paper 1), which typically indi-cates slag tapping practices (Killick 1990; Chirikure and Rehren 2006a; Miller and Killick 2004). The concentration of furnace bases at this site represents large-scale iron production suggestive of a market beyond subsistence con-sumption.

4.3 Evidence from archaeological field surveys and excavations

Twenty-six new iron-working sites and fifteen others from previous archaeo-logical surveys were recorded around the Great Zimbabwe urban centre (Ta-ble 1 in Paper 1). The majority of these sites had double fused tuyeres, some with as many as ten tuyeres fused together by slag (Paper 1). Almost all of the iron working sites were found located on the west side of granite landscape features such as whale-backed hills, bornhardts, kopjes and tors, and anthills in some cases, a behavior noted among the Tumbuka of central western Ma-lawi (Killick, 1990) and Fipa of southwestern Tanzania (Mapunda, 2010). Hu-mans are known to be creatures of culturally patterned behaviour (Hodder and Orton, 1976), and as I shall argue later in the discussion, the recurrent location of iron production activities west of boulders and anthills would have been both symbolical and practical (see also Mapunda, 1995).

56

Figure 8. A dense concentration of tuyeres in the excavation trench at Chigaramboni iron production site. Note that the frame is one square metre. (Photo by Webber Ndoro, 1991)

Figure 9. Tuyere-moulded slag from Mashava iron production site (Photo by author, 2015)

57

4.3.1 Boroma Excavations The excavations at Boroma Site recovered iron slag, broken tuyere pieces, furnace rubble, and charcoals. The bulk of slag from the Trench 2 was made up of large cake-like blocks, the largest one measured about 15 x 13 cm, and a thickness of about 7 cm, suggesting that these were furnace slag. Some of these blocks had plant impressions and possible bone inclusions. Trench 3 yielded small slag pieces of amorphous shape measuring 3 x 2 cm on average. The slag had very low magnetism and was very porous. At least 30 broken tuyere pieces measuring at most 15 cm in length were recovered from Trench 2. A maximum of four broken tuyere pieces were found fused together, sug-gesting that the smelting process used natural draft air-supply mechanism (Figure 8). Both single and multiple-fused tuyere exhibited evidence of vitri-fication and collapse at the distal end, indicating that these were inserted deep into the furnace where they were affected by very high temperatures. The in-ternal diameter of the different tuyere recovered at Boroma site ranged be-tween 30 and 40 cm, while their external diameter measured between 50 and 60 cm.

Figure 10. Boroma excavation archaeometallurgical materials: Multiple fused tuy-eres (left); Plant impressed slag (right) Photo by author, Field Data (2013)

4.3.2 Veza 1 Excavations A semi-circular furnace wall measuring 100 cm in diameter, with a plastered base tilting gently westwards was uncovered in association with multiple fused and a single tuyere. The western section of the furnace wall had been totally removed, probably by the ancient metallurgists themselves as a way of harvesting the bloom from the furnace chamber. A possible rake channel was also uncovered sloping down to the west from the furnace and continuing be-yond the main trench, which necessitated an extension on the southwestern corner measuring 1x1m. This structure measured about 50 cm wide and at least 120 cm long. Charcoal samples were collected from a cluster of tuyeres on the floor of the furnace for purposes of radiocarbon dating and wood spe-cies identification. The tuyeres had an average internal diameter of about

58

3.5cm, a wall thickness of about 1.5 cm and length of about 20 cm. At least two tuyeres were found fused together with evidence of vitrification and melt-ing at the distal end, indicating that they were exposed to very high tempera-tures deep inside the furnace during the smelting process. The excavations also yielded possible smithing slag characterized by plano-convex shape, co-existing with smelting slag in the same locality.

4.3.3 Mutevedzi Excavations A rectangular furnace base was uncovered in association with at least twenty tuyere was uncovered. The furnace wall, which was about 15 cm thick, had visible finger impressions, vitrification evidence of possible leakage. The floor of the furnace sloped gently northwards and the southern end of the fur-nace was destroyed. The furnace base, which measured about 2 x 1 showed evidence of slag leakage through the cracks in its 10 cm thick wall. The rec-tangular furnace base is a unique design discovered at Mutevedzi site. It is unclear whether this furnace was once similar to the one described under Veza 1 above. At least 20 tuyeres were found arranged by the side of the furnace base as if kept for recycling. Almost all of the tuyeres had signs of vitrification with an average length of 25cm. At least three tuyeres were found fused to-gether, showing signs of total collapse and melting on the end closest to the fire bed (Figure 10). The slag recovered from the excavation had very high porosity and straw impressions, with some of them exhibiting near-straight edges from the shape of the furnace. The slag had very low magnetism.

Figure 11. Archaeometallurgical Remains from Mutevedzi Site: Tuyeres fused in multiples (left); Plant impressed slag with straight edge. Photo by author, Field Data (2014)

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4.4 Results for chemical and microstructural analyses The detailed archaeometallurgical results are given in Paper II, and here I give a condensed summary.

4.4.1 Mashava The bulk chemical composition analyses reveal a low average content of iron oxide (57 wt%,) a very high content of silica (38 wt% ) and as low as 3.6 wt% alumina for samples Mas1 and Mas2, relative to the range established for bloomery iron technology (Morton and Wingrove, 1969). Such a low iron ox-ide content commonly indicates an efficient iron smelting process (Iles and Martinón-Torres, 2009), while the low amount of alumina underpins that the sample originated from tap slag. This confirms the flow structure observed during macroscopic examination of the two samples. The observed high silica levels silica content usually indicates a deliberate addition of sand to slag-metal separation particularly for high grade iron ore such as magnetite (e.g. Killick and Miller, 2014). Microstructurally, slag samples from Mashava site are distinct, characterized by well-crystallized and very fine-skeletal fayalite grains in a glassy matrix and angular magnetite, which further supports the observation that this is tap slag. Again, sample Mas1 has evidence of a bright continuous line of magnetite, which forms when slag cools and crystallizes rapidly in oxiding conditions outside the furnace (see Figure in Paper IV). Slag tapping techniques is considered a novel process in preindustrial iron metal-lurgy, which made it possible to smelt the ore for longer periods without blocking the flow of combustion air through the tuyeres into the furnace. The slags are also constituted by well-crystallized fayalite, representing well-con-trolled reducing conditions and intense heat capable of transforming as much iron ores as possible into metallic iron (Buchwald, 2005).

4.4.2 Mutevedzi The results for the chemical analysis of Mutevedzi slag reveal that it has the lowest content of iron oxide (about 43 wt%), the highest level of manganese oxide (almost 12 wt%) and a relatively high silica content (26 wt%), as shown in Table 3 in Paper II. It also has as high 8 wt% alumina content, more than 3 wt% calcium oxide, the highest reading in of all the analysed samples in this study, and has more than 2 wt% magnesium and potassium oxides. As com-monly encountered elsewhere, slags with such a high content in manganese oxide often indicate an efficient slag-metal separation process (Chirikure and Rehren, 2006a; Iles, 2014; Pleiner, 2000). Charlton et al. (2010: 353) explain that non-ferrous oxides such as manganese and calcium tend to substitute iron oxide as a flux for silica, which improves the yield of metallic iron. They also note that amounts of alumina above 5 wt% often increases a slag’s melting

60

temperature and viscosity. Mutevedzi slag has very little wustite in its micro-structure characterized by the predominance of fayalite and wustite. In sum, both the slag chemistry and microstructure of Mutevedzi reveal a high level of skill in the past metallurgists in manipulating bloomery recipes and pro-cesses. Interestingly Mashava slag samples have the lowest manganese con-tent (0.43 wt%), indicating significant variations in the technological ap-proaches used at Mutevedzi, whose slags show no evidence tap slag.

4.4.3 Boroma Boroma slag is chemically and microstructurally related to Mutevedzi than Mashava particularly sample Bor2 with as low as 55 wt% iron oxide as high as 11.7 wt% manganese oxide (see Table 3 in Paper IV). There is also a no-ticeable amount of alumina in all the three samples analysed, more than 5 wt%. The microstructure of the samples is dominated by fayalite, leucite and her-cynite, very few iron prills and a small amount of wustite. As observed and explained under Mutevedzi above, the high content of manganese and alumina in the slag samples indicate that these oxides would have been critical in achieving an efficient slag-metal reaction process and the formation of molten slag. According to Smedley et al. (2001) and Stern et al. (2004), wood selected for metallurgical purposes are at times rich in lime, potash and magnesia and manganese having taken these minerals from a habitat and geology rich in such elements. While this may be true for the other elements, the manganese levels in the slag samples of Boroma and Mutevedzi sites are too high to be explained in this way. It is most likely that smelters at the two sites exploited a manganese rich iron ore or fluxes as suggested by Iles (2014) and Pleiner (2000), which would explain their difference with Mashava site, where mag-netite was presumably smelted (Mtetwa, 2011).

4.4.4 Sviba The dominant chemical elements in Sviba slag are iron oxide (about 67 wt%), silica (25 wt%) and alumina (about 6 wt%). All the other oxides are below 1 wt%, revealing a significant difference from the slag chemistry of Mashava, Mutevedzi and Boroma above. Its microstructure of the slag reflects a miner-alogical composition characterized by a dominant fayalite phase, dendritic wüstite and hercynite and subordinate leucite (see Figure in Paper II). The ab-sence of noticeable trace elements in Sviba slag suggests that the smelters at the site may have added no fluxing materials into furnace. Rather, the smelters would have relied, most likely, on clays rich in silica or intentionally mixed with sand to make furnace lining and tuyeres to survive as both refractory materials and sacrificed in slag formation, a practice commonly encountered in preindus-trial iron metallurgy (Chirikure, 2015; Veldhujzen and Rehren, 2014). In such situations, as noted by (Charlton et al., 2010), silica reacts with iron oxide to

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form a ferrosilicate slag at temperatures above 1200°C, a process that enhanced the slagging process, but reduced the yield of metallic iron. This is a reasonable explanation for the relatively high content of iron oxide, silica and alumina ob-served in the slag chemistry of Sviba site, with alumina being critical for in-creasing the melting temperature and viscosity of the slag.

4.4.5 Veza A Site Two samples, VezA1 and VezA2, were analysed from Veza A site. The chem-ical analysis result for sample VezA1 reveal a considerably high content of iron oxide (71 wt%), and a relatively low amount of silica (17 wt%) and alumina (3.5 wt%). With the exception of magnesium and calcium oxides, which have around 1 wt%, all the other oxides namely titanium, manganese, magnesium, calcium, sodium, potassium and phosphorus are below 1 wt%. The high amount of iron oxide is also reflected in the microstructure of the sample in the form of dendritic wustite. There are also remnants of the metallic iron in the microstruc-ture, which explains why the sample is magnetic (see macroscopic attributes in Table 2 and the photomicrograph in Figure in Paper II). The microstructure also reveals blocky fayalite indicative of slow cooling of the slag in non-oxidizing conditions inside the furnace, which confirms the sample as a piece of iron smelting slag. However, sample Veza2, which has a plano-convex morphology macroscopically, has a higher iron oxide content of 76 wt%, very low silica content of 9 wt% and alumina content as little as 2 wt%, which classifies it as smithing slag (see Serneels and Perret, 2003). This is a reasonable conclusion, given that there is no further contribution of silica from furnace lining and tuy-eres in a smithing in hearth, which is usually an open fireplace. The presence of smelting and smithing slag at Veza 1 provides a crucial window into under-standing variation and change in the spatial organization of technology, a point that I will pick for elaboration in the discussion chapter.

4.4.6 Veza B Site Although this site is located barely 2 kilometres away from Veza A along the same stream, it has a distinct chemical composition and microstructure. Chem-ically, sample VezB1 has an iron oxide content of 66 wt%, silica content of 17 wt %, about 4 wt% of alumina and a noteworthy 5 wt% manganese. The chemical results also reveal a noticeable presence of such oxides as magne-sium, calcium and potassium above 1 wt%, which are usually introduced into the smelt from the fuel ash, as observed elsewhere (Chirikure, 2005; Smedley et al., 2001; Stern et al., 2004). The low levels of alumina in the sample sug-gest the possible use of slag tapping techniques at the site as observed at Baranda site in northern Zimbabwe (see Chirikure and Rehren, 2006). How-ever, the absence of well-crystallized and very fine-skeletal fayalite grains in the microstructure of Veza 2 slag makes such a possibility very unlikely. The

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mineralogical composition shows a high presence of wustite, fayalite, glass, leucite as well as droplets of metallic iron.

4.4.7 Chigaramboni Two samples were analyses from Chigaramboni site, Chi1 and Chi2. The chem-ical composition of Chi1 is dominated by iron oxide (c. 67 wt%), silica (c. 20 wt%), manganese (c. 7 wt%) and alumina (c. 5 wt%). The sample is also com-posed of noticeable amounts of magnesium (c 2wt%), calcium (c. 3 wt%) and potassium (2 wt%). As noted ugnder Mutevedzi, Boroma and Veza B sites, the enriched levels of manganese mostly derive from the type of ore exploited at these sites. Similarly, alumina would have increased slag’s melting temperature and viscosity, as explained by (Charlton et al., 2010). The tendency for manga-nese to enhance the slag-metal separation process means that such an ore would have preferred ahead of other options, which raises questions regarding the pol-itics of inclusion and exclusion from access among contemporary users, a dis-cussion that I will return to in the next chapter. Such elements such as calcium and potassium usually derive from fuel ash, and there seems to be a set of par-ticular trees that produce such fuel ash, which possibly made them coveted re-sources. The microstructure of Chi1 is dominated by fayalite, dendritic wustite and droplets of metallic iron, which explains why the slag is magnetic, among other physical properties highlighted in Table 3 in Paper II.

Sample Chi2, on the other hand, has the second highest content of iron oxide (c. 91 wt%), and the lowest amount of silica (c. 5 wt%), alumina (c. 1 wt%), a noticeably high content of manganese (c. 4 wt%) and magnesium (c. 2 wt%). All the other elements fall far below 1 wt%. Its microstructure shows a complex combination of wustite-magnetite and interstitial glass. A wustite-magnetite combination suggests that this sample derived from furnace slag, which was close to the mouth of tuyeres where it cooled under partially oxidizing condi-tions.

4.4.8 Goose Bay The chemical result for Goose Bay slag reveals the highest content of iron oxide (c. 95 wt%) and very low silica (c. 8 wt%) and alumina (c. 3 wt%). The rest of the elements analysed in this study for Goo1 are far below 1 wt%. Its microstructure shows blocky fayalite, dendritic wustite and interstitial glass. The blocky fayalite suggests that this sample derived from furnace slag. The high iron oxide suggests that the slag-metal separation process was not very efficient, most likely because of very little silica and alumina. As observed at the other sites, silica is crucial for the slagging process, while alumina is equally essential for increasing the slag’s melting temperature (Buchwald, 2005; Charlton et al., 2010). Macrophysically, Goo1 is dense, heavy and has

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a metallic grey streak all around the sample, with one of its sides being mod-erately magnetic.

4.5 Evidence from Anthracological analysis The aim of the anthracological analysis was to identify all the studied frag-ments to the level of their species. This data has not been presented elsewhere and therefore I will detail the result here. At least five taxa made up the species diversity of trees selected in the iron production activities largely for wood charcoal fuel and possible technomedicines. These include Dichrostachys ci-nerea, Julbernardia globiflora, Brachystegia, Acacia and an unidentifiable one. The iron smelters at Boroma site seem to have exploited all the identified taxa, with the exception of the Brachystegia genus, which is missing in the assemblage. Acacia polyacantha occurs at two of the three sites that yielded is the commonest taxa, followed by Dichrostachys cinerea. Boroma is the only site showing the occurrence of Julbernadia globiflora while Veza A is the only one with the Brachystegia genus. Goose Bay is second in terms of species diversity, showing a bias towards Dichrostachys cinerea and Acacia polyacantha. The popularity of these two tree species in the iron industry of Boroma and Goose Bay sites is noteworthy, as shall be detailed in the follow-ing discussion chapter.

Table 4. Tree species identified from archaeological charcoals found in association with iron production sites around Great Zimbabwe

Site Name

Charcoal Samples

Number of Tree Species Identi-fied

Identified Genus and Species

Boroma 82 3 Dichrostachys cinerea, Julbernadia globi-flora and Acacia

Goose Bay

13 2 Dichrostachys cinerea and Acacia.

Veza A 33 1 Brachystegia

4.5.1 Boroma Site Under reflected light microscopy, specimen 1 from Boroma Trench 2 showed ray cells that are crystallized and heterogeneous. The ray cells are also square, procumbent and upright. The parenchyma is 3 cells wide. Rays are 1-3 seriate. Radial multiples of 2-3 occur. Solitary vessel arrangement occurs as well. The specimen is however, predominantly radial multiple, which suggests that this is Dichrostachys cinerea (Figure 3A). As a species, D. cinerea has a wide range of uses. Because it burns slowly and well, it is a favorite of metalworkers as an excellent source of fuel (Palgrave 2002). Its roots and leaves are used to

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treat snakebites and scorpion stings including sore eyes and toothaches (van Wyk and van Wyk 1997). Its hardness makes it perfect for tool handles such as axes, hoes and ceremonial spears. In ecological studies, the tree species is regarded as an indicator of overgrazing and impoverished ground (Drummond and Palgrave 1973; van Wyk and van Wyk 1997).

Specimen 2 from the same site and trench as specimen 1 above showed solitary vessel arrangement, rectilinear parenchyma, and banded parenchyma 2-4 cells wide under the microscope (Figure 3B). The rays are 2-5 lines, semi-ring porous and square to upright, mixed cells, Procumbent, TLS (E-F): 4; 5 cells wide, heterogeneous ray cells, pitted fibers, more than 4 cells wide, sug-gesting that this is Acacia species (see Chikumbirike 2014). This species pro-duces wood of high density, about 800-890kg/m³ and makes excellent char-coal. Its firewood generates a lot of heat and burns very evenly and cleanly with little smoke a favourite of many families in southern African (Timberlake et al 1999). Like the other tree species, it was used in many other social con-texts including medicine where traditional healers treat general body pains, dizziness, convulsions, diarrhoea and it is used as an aphrodisiac. In Zimba-bwe, peasant farmers lace its roots in the chicken run to control parasites, while its barks are used to treat poisoned cattle (Chikumbirike 2014).

A B

Figure 12. Photomicrograph of charcoal specimen from Boroma Site Trench 2: (A) shows the microstructure of Di-chrostachys cinerea; (B) shows the mi-crostructure of Acacia species; (C) shows Julbernadia globifora. (Photo by Joseph Chikumbirike, 2017).

C

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The analysis of specimen 3 from Boroma site, Trench 2 level 4, reflected 1-2 seriate and banded parenchyma. The vessel arrangement are solitary with ra-dial multiples of 2 showing procumbent cells, while the rays are 1-3 cells wide and crystalliferous (see Figure 12C), suggesting that this is Julbernardia glo-biflora. This tree species occurs in miombo woodland alongside Brachystegia spiciformis. It is used as a general-purpose timber and for making mortars for crushing grains especially maize (Palgrave 2002).

4.5.2 Veza A Site Under optical microscopy, the vessel arrangement of this specimen are exclu-sively solitary. The rays are uniseriates and its cells appear crystallized. There is a line of parenchyma, 7 vessels per square millimeter. It also exhibits a banded parenchyma. The rays are uniseriates and are 8 cells long. The speci-men is identified as the family of Caesalpiniaceae and possibly the Bra-chystegia genus (see Figure 12). The Brachystegia genus is suitable for gen-eral-purpose timber and firewood (Chikumbirike 2014). Its roots are used as a medicine for treatment of dysentery and diarrhoea. Furthermore, a decoction is applied to the eyelashes to treat conjunctivitis, which reflects how trees were used in wide range of social contexts (van Wyk and van Wyk 1997).

4.5.3 Goose Bay Site Charcoal samples from Goose Bay exhibited similarities with specimen 1 of Boroma site charcoal samples. Under reflected light microscopy, the specimen revealed radial multiples 2-3, confluent to banded parenchyma, rays are 1-3 ray lines, Aliform parenchyma. The TLS are 2 cells wide, have short vessels, and 3 wide heterogeneous ray cells. They also are square to procumbent on the margins, procumbent in the middle and inside the rays. Like the Boroma specimen (see Figure 12A), the specimen was identified as Dichrostachys ci-nerea (Figure 12B).

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Figure 13. Photomicrograph of the charcoal specimen from Veza A identified as the family of Caesalpiniaceae and possibly the Brachystegia genus. (Photo by Joseph Chikumbirike, 2017).

A

B

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5 Discussion

Here, I will summarize the results in relation to questions regarding the organ-ization of technology, its variability as well as human-environment interac-tions raised in the introductory chapter.

5.1 Spatial and social organization The results from both macroscopic and microscopic analyses show that the spatial organization of industrial activities in the wider archaeological land-scape of Great Zimbabwe was more varied and ambiguous than previously asserted. Iron smelting, usually associated with ritual performances and the rhetoric of human procreation, is generally suggested to have taken place out-side settlements in seclusion from women, children and strangers (e.g. Childs and Killick, 1993; Huffman, 2001, 1986). The co-existence of smelting and smithing slags at Veza A site, however, demonstrate that such rigid separation of these two activities in space was not always the case (see also Chirikure and Rehren, 2006). Interestingly, iron production debris from Boroma and Goose Bay sites underpin smelting and smithing activities within domestic contexts, as observed also in the Great Zimbabwe urban centre itself (see Bandama et al 2016; Fredriksen and Chirikure 2015; Herbert, 1996; Miller 2002).

The varied spatial organisation revealed suggests an intimate link between iron technology and the dynamics of social power relations amongst the Great Zimbabwe inhabitants. It has been assumed, previously, that the elite con-trolled iron production in the entire empire (Herbert, 1996). This notion pro-jected the Great Zimbabwe society as a highly centralised society in which the rulers made decisions regarding the daily activities associated with the spe-cialised production of artefacts and materials. I would argue, however, that the presence of archaeometallurgical remains within domestic contexts suggests the existence of independently organised production across the wider archae-ological landscape of Great Zimbabwe. It suggests that technology was prob-ably less controlled than once thought, and practiced across social groupings outside of elite control. Large-scale iron production activities were also ob-served outside settlement, e.g. at Mashava and Chigaramboni. Considering the observed technological variation in space and time, such large-scale produc-tion would have run under self-organized specialists who had the flexibility to

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make decisions on iron related practices (see similar discussion in Hjärthner-Holdar & Risberg 2009: 983). Indeed, such specialists would have paid tribute to the rulers for continued support of their activities (see Mudenge, 1988). Such tribute would have taken the form of finished iron products, raw materi-als or even labor, as suggested the cache of iron hoes, iron ore and varied other metal objects found at Great Zimbabwe (see detailed review in Chirikure and Pikirayi, 2008).

Furthermore, the location of iron production within the domestic arena pro-vided a context in which women and possibly children would have been so-cialized into, or negotiated their way into the world of iron. Likewise, the ex-istence of iron metallurgy in the domestic sphere also meant that there was a mutual influence with other social practices and worldviews as evidenced such decorations as female anatomical organs, which could be found also on houses, pots, drums and headrests (Chirikure, 2005; Collett, 1993). This way of viewing these decoration crossovers has the potential to provide an alterna-tive reading of iron technology in which female agency is far more prominent than what has previously been realized. Within such household industries (DeMarrais, 2013; Hirth, 2009), iron production would have directly involved the collective effort of all able-bodied family members in all metallurgical activities ranging from gathering of raw materials to distribution of the iron metal.

The modern-day case of Mbuya Murozvi’s home-based smithing activities dealt with in Paper IV is a classic example demonstrating how a female agent through social negotiation and appropriation of iron smelting became a chief smith within an industry largely viewed as a male domain. An inclusive in-volvement of varied social agents beyond the male gender in iron technology could be considered for the iron smelting activities located also outside settle-ments. Spatial variation does not necessarily suggest a different belief system between smelting inside and outside settlements (see discussion in Fredriksen and Chirikure 2015). The entire process of iron production is, in itself, is a collective enactment of materials and disparate esoteric knowledge and know-how, which are usually embodied in different individuals.

5.2 Technological variability The results show the existence of a remarkable variety of iron production tech-nologies that developed and changed over time. The area has concentrations of iron production sites intimately correlated with the mountain ranges sur-rounding the urban centre, illustrating the social and physical use of the land-scape. These remains point to a wide range of novel designs and processes of metal extraction in the form of natural draft furnaces, tap slags and a rectan-gular furnace design previously unknown in the iron metallurgy of southern

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Africa. The discovery of tap slag at Mashava site, confirmed by both macro-scopic and microscopic analyses, has significantly advanced our knowledge of the technology and processes of iron production south of the Zambezi River.

In addition, there is now a growing corpus of evidence pointing to the use of natural draft iron smelting technologies at several sites in the form of tuy-eres fused in multiples and large concentrations of wide furnace bases. The presence of large natural draft furnaces in the Chigaramboni hills, Mashava, Boroma, Mutevedzi and Veza sites represents a significant change in technol-ogy intimately linked to transformations in the social, economic and environ-mental systems and processes of Great Zimbabwe. The large capacity of nat-ural draft furnaces, for instance, point to the existence of large-scale trade in improved quantities and quality of iron at the zenith of intensified links with the Indian Ocean trade community (see similar discussion in Cline, 1937). As such, it would seem more likely that the coveted iron from the interior of southern Africa traded along the Mozambican Coast during Al Idrisi’s visit in 1154 derived from the iron industry of Great Zimbabwe.

Interestingly, two sites with tuyeres fused in multiples have been radiocar-bon dated to the early second millennium AD, making Great Zimbabwe one of the earliest known areas with evidence of natural draft technology in south-ern Africa (for other examples see Chirikure and Rehren, 2006b; Prendergast, 1979). As such, the dates offer a new chronological frame to rethink the dis-tribution and circumstances surrounding the development of natural draft technology in Sub-Saharan Africa. Proximity to the urban centre and dating suggest linkages with the metal extraction strategies of Great Zimbabwe itself, which was at its peak between the 12th and 16th centuries AD. So far, the use of huge natural draft furnaces in the technological history of the world’s pre-modern societies is considered a possible independent invention in sub-Sa-haran Africa. The furnaces, driven by air sucked in at the base as buoyant hot air rises through the chimney (Rehder, 2000), freed much human labor from the pumping of bellows, which represents a significant mechanical and social advantage over forced draft technology. Apart from consuming large volumes of charcoal, the long smelting hours in natural draft furnaces also promoted the diffusion of carbon into iron, which would have produced high-quality steel blooms (see Cline, 1937; Killick, 2015, 1991).

Thus, there is a new emerging understanding of iron production in and around Great Zimbabwe. More detailed fieldwork, however, is required spe-cifically to recover more high quality material for chronometric dating and archaeometallurgical analyses. In particular, we still know very little regard-ing the chronology, distribution and circumstances leading to the use of a rec-tangular furnace design similar to that excavated at Mutevedzi. All historic rectilinear furnace designs are widely reported in southeast Asia (G Juleff, 2009; G. Juleff, 1996; Tabor et al., 2005), which raises questions regarding

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possible cross-borrowing of technological ideas in trade and social interac-tions between Great Zimbabwe and other parts of the distant world. In addi-tion, lead isotope and elemental analyses of metal objects and the geochemis-try of the exploited iron ores (e.g. Ling et al., 2014), for instance, have the potential to yield insights into the connections and disconnections between the Great Zimbabwe urban centre and the metallurgical resources and technolo-gies across its wider archaeological landscape. These methods have not been included in this thesis, but should be developed in the future.

5.3 Variation and change in resource exploitation patterns

The results of anthracological analysis, coupled with information solicited from village elders, bring out an intimate interaction between the Great Zim-babwe inhabitants and their biophysical environment. With an estimated pop-ulation of about 10 000 inhabitants during its zenith period (see detailed review in Chirikure et al., 2017), Great Zimbabwe would have required vast amounts of wood resources for both domestic and metallurgical purposes. Its importance as a political and religious centre, and as the main interior hub of the Indian Ocean and Central African trade systems (Pikirayi, 2017) is likely to have resulted in an ever-increasing demand for improved quantities and quality of iron.

In Great Zimbabwe and many other places, the size and organization of production (Costin, 1991), was a key factor for the location of industrial ac-tivities. The large natural draft furnaces identified in the Great Zimbabwe area tended to be located away from settlements. One reason for this could be that the hinterland offered a variety of desired tree species and in larger quantities of charcoal fuel than closer to the center. In interviews with village elders liv-ing around Great Zimbabwe, residents stated that proximity to wood resources was usually the decisive factor in locating large-scale iron production activi-ties. The logic behind was that, of all the raw materials required for iron smelt-ing, wood charcoal was the bulkiest and most fragile, making charcoal un-practical to transport it over long distances. Thus, the quantity and location of desired wood species was integral in shaping the social engagements between people and their material world in Great Zimbabwe. The discussion is relevant for our understanding of Great Zimbabwe environment. As reviewed in the introduction many researchers have argued that the environment around Great Zimbabwe became degraded over time. There are still no or little environmen-tal data, however, to test this hypothesis.

Anthracological analysis carried out within the frames of this thesis has indicated that iron producers selectively exploited a range of tree species for the production of wood charcoal to fuel metallurgical processes (see summary

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results section). Out of 149 tree species recorded from the modern flora in the Great Zimbabwe area by Chikumbirike (2014), four taxa namely Dichrosta-chys cinerea, Julbernardia globiflora, Brachystegia, Acacia have previously been identified as linked to the iron industry. From the charcoal assemblages presented here, the iron smelters at Boroma site seem to have exploited all the identified taxa, with the exception of the Brachystegia genus that is rare. Aca-cia occurs at two of the three sites that yielded is the commonest taxa, followed by Dichrostachys cinerea. Boroma is the only site showing the occurrence of Julbernadia globiflora while Veza A is the only one with the Brachystegia genus. The lack of Brachystegia on the sites analysed here could possibly sug-gest that this species was becoming increasingly rare due to exploitation. Amongst the miombo trees, Julbernardia appears to be favoured over Bra-chystegia with intensive exploitation (Ekblom et al in press). However, the charcoal analysis previously presented by Chikumbirike (2014), does not sug-gest temporal differences in selection of species. Thus, even though Bra-chystegia may have been locally rare or less preferred for iron production as may be suggested here, the changes observed by Bannerman (1982) with a near absence of both Brachystegia and Julbernardia must have been a late occurrence in history.

Apart from wood charcoal fuel and the iron ore itself, iron production also required flux materials for successful slag-metal separation. The slag chemis-try of Boroma site, which exhibited close resemblances with that of Muteve-dzi, Veza B and Chigaramboni (see Paper III), revealed enriched levels of such fuel ash oxides as calcium and potassium. These flux materials, possibly added as ritual medicines common in African iron metallurgy, point to the embeddedness of iron related practices in the efficacy of everyday belief sys-tems (Schmidt, 2009a; Warnier, 2009). Calcium and potassium, which could have been provided from fuel ashes, but also bones, are good flux materials known for substituting iron oxide for silica, which improves the yield of me-tallic iron (Charlton et al., 2010). A block of slag from Boroma site, for in-stance, exhibited bone inclusions, which could have been deliberately charged into the furnace to decrease the melting temperature of the slag as part of the bloomery recipes, as evidenced elsewhere (De Caro et al., 2013; Prendergast, 1974; Summers, 1958). Thus, the iron technology of Great Zimbabwe, just like its drystone architecture which incorporated natural boulders into the wall fabric (Pikirayi, 2013), is characterized by an intimate social engagement be-tween the people and their biophysical world.

The last but not least point to consider is the ever-growing interest regard-ing the possible effects of iron production on albedo and consequently on local climate (Ekblom et al, in press; Iles, 2016; Li et al., 2011; Schmidt, 1994). The discovery of natural draft furnaces in the Great Zimbabwe landscape during the course of this study adds further concern regarding the outtake of wood resources to meet the high demand for wood charcoal fuel in the iron industry. This realization is based on the point that although natural draft furnaces were

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very economic in terms of labor, they are said to be expensive in fuel con-sumption (Killick 2015; 1991; 1990). The charcoal sample analysed in this study is rather small and from few sites to shed adequate light regarding this concern. It does suggest, however, the use of tree species indicative of signif-icant changes in the nature and condition of the environment. The dominance of Dichrostachys cinerea as charcoal fuel in the analyzed sample, for instance, is understood in ecological studies as indicative of an opened landscape and forms secondary bush that grows in impoverished ground (see van Wyk and van Wyk 1997; Venter et al. 1996; Drummond and Palgrave 1973). Further-more, there is a reduction in the number of tree species exploited at Goose Bay site, dated to the historical period, as compared to Boroma site dated to the early second millennium AD. It is not clear whether this reduction in tree spe-cies selected for use in the iron industry reflects environmental degradation or a matter of cultural choice during the period of Goose Bay Site. It would seem more likely that such a change in wood harvesting practices in the iron indus-try of Great Zimbabwe was in response to a modified environment. The im-portance of this study is that it indicates the effects of human-landscape inter-actions at a local scale.

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6 Conclusion and future research

The results of this study shed significant and new light on varied aspects con-cerning the nature and organization of industrial activities that critically influ-enced and were equally influenced by the sociopolitical transformations of Great Zimbabwe over time. Importantly, they illuminate the role of ironwork-ers as crucial agents in establishing the social networks of places and other producers who were under the influence of Great Zimbabwe. These embodied social agents were critical in the production of social space and materials that shaped and were shaped by the everyday life experiences in Great Zimbabwe. The study’s illumination of the iron metallurgy in the wider archaeological landscape also brings forward the intimate social engagements that would have sustained the urban itself in dynamic social networks.

Furthermore, the discovery of more evidence underpinning the widespread use of natural draft furnaces point to the existence of large-scale industrial iron production in Great Zimbabwe at some time in the past, at present one of the earliest known in Southern Africa. Contrary to earlier views, the range of ar-chaeometallurgical material explored represent significant technological in-novation and novel designs and processes of metal extraction in the form of slag tapping in further south of the Zambezi River in southern Africa. The iron production debris also suggests the co-existence of primary and secondary metal extraction in domestic and specialized settings outside settlements. These remains suggest varied scales of decentralized production involving household craft activities co-existing with the much large-scale industrial ex-traction of iron.

Within such decentralization, household production could point to internal trade amongst the inhabitants of the Great Zimbabwe area alongside large-scale production well adapted for extensive trade networks. Such household industries would have played a significant role in adapting to disconnections of the Great Zimbabwe state from global trade (Mtetwa, 1976; Pikirayi, 2017). Most importantly, the social memory of indigenous iron metallurgy curated within household industries continue to play a critical role in adapting to and surviving the collapse of Zimbabwe’s economy since the dawn of the 21st cen-tury AD (Mtetwa et al 2016; Hjärthner-Holdar 1998).

Finally yet importantly, the study also illuminated how iron technology could also be appropriated to challenge gender roles. The domestic context of iron production would have provided a social space in which the control of

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esoteric knowledge of iron technology would have been appropriated and ne-gotiated across the gender and age axis. Using the case study of modern iron smithing near the Great Zimbabwe site, the study illustrated how a female chief negotiated her way into iron production usually viewed as a male do-main. In so doing, the thesis brought forward the significance of iron in the large-scale social, economic, political and environmental systems and pro-cesses of Great Zimbabwe.

Although this study has illuminated significant aspects regarding the ar-chaeologies of Great Zimbabwe’s iron, there is need for further research. The lack of chronology for most of the studied iron production sites, for example, is a major weakness of this thesis. In the absence of dates, relative or chrono-metric, the only other variable suggestive of an association between the urban centre itself and sites in the hinterland is proximity. Proximity is a rather in-secure link, seeing that metalworking communities have occupied the land-scape around Great Zimbabwe from the early first millennium AD to the pre-sent. Any site can fall within that very broad range. Further excavations of industrial sites should strive to recover materials dateable by such methods as thermoluminescence. Again, chronology is very crucial to determine when the unique rectangular furnace, which was discovered during the course of this study, might have been introduced in the history of Great Zimbabwe.

There is also a need to conceptualize the newly illuminated iron technology of Great Zimbabwe within the broader context of connections and disconnec-tions between southern Africa, the Indian Ocean and central African trade sys-tems. So far, the archaeology of these technologies, which were critical in the production of the traded metals, have been treated independently (e.g. Chiri-kure 2005; Killick 1990; Mapunda 1995; Mtetwa 2011; in press). This down-plays the possible inter-regional cross borrowing of technological expertise, ideas or even technicians over time and space. Such a research has the poten-tial to shed significant light on the adaptation and adoption of metal technol-ogy within and beyond Africa. The existence of a rectangular furnace in the Great Zimbabwe landscape as reported in Paper I, requires comparative ex-amination with similar structures in South-East Asia, a component of the In-dian Ocean trade network community.

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